We Keep Coding

Determine whether each character in the first string can be uniquely replaced by a character in the second string so that the two strings are equal

Give two strings of equal size. Determine whether each character in the first string can be uniquely replaced by a character in the second string so that the two strings are equal. Display also the corresponding character pairs between the two strings. The code works well now.
Example 1:
For input data:
aab
ttd
The console will display:
True
a => t
b => d
Example 2:
For input data:
tab
ttd
The console will display:
False
In the second example the answer is false because there is no unique correspondence for the character 'a': both 't' and 'd' correspond to it.
This is my code:
using System;
namespace problemeJM
{
class Program
{
static void Main(string[] args)
{
string firstPhrase = Convert.ToString(Console.ReadLine());
string secondPhrase = Convert.ToString(Console.ReadLine());
string aux1 = string.Empty, aux2 = string.Empty;
bool x = true;
for (int i = 0; i < firstPhrase.Length; i++)
{
if (!aux1.Contains(firstPhrase[i]))
{
aux1 += firstPhrase[i];
}
}
for (int i = 0; i < secondPhrase.Length; i++)
{
if (!aux2.Contains(secondPhrase[i]))
{
aux2 += secondPhrase[i];
}
}
if (aux1.Length != aux2.Length)
{
Console.WriteLine("False");
}
else
{
for (int i = 0; i < firstPhrase.Length - 2; i++)
{
for (int j = 1; j < secondPhrase.Length - 1; j++)
{
if (firstPhrase[i] == firstPhrase[j] && secondPhrase[i] == secondPhrase[j])
{
x = true;
}
else if (firstPhrase[i] != firstPhrase[j] && secondPhrase[i] != secondPhrase[j])
{
x = true;
}
else if (firstPhrase[i] == firstPhrase[j] && secondPhrase[i] != secondPhrase[j])
{
x = false;
break;
}
else if (firstPhrase[i] != firstPhrase[j] && secondPhrase[i] == secondPhrase[j])
{
x = false;
break;
}
}
}
Console.WriteLine(x);
aux1 = string.Empty;
aux2 = string.Empty;
if (x == true)
{
for (int i = 0; i < firstPhrase.Length; i++)
{
if (!aux1.Contains(firstPhrase[i]))
{
aux1 += firstPhrase[i];
}
}
for (int i = 0; i < secondPhrase.Length; i++)
{
if (!aux2.Contains(secondPhrase[i]))
{
aux2 += secondPhrase[i];
}
}
for (int i = 0; i <= aux1.Length - 1; i++)
{
for (int j = 1; j <= aux2.Length; j++)
{
if (aux1[i] == aux1[j] && aux2[i] == aux2[j])
{
Console.WriteLine(aux1[i] + " => " + aux2[i]);
break;
}
else if (aux1[i] != aux1[j] && aux2[i] != aux2[j])
{
Console.WriteLine(aux1[i] + " => " + aux2[i]);
break;
}
}
}
}
}
}
}
}

I think you should use a Dictionary<char, char> as commented. But you need to check if there's a unique mapping in both string, so from s1 to s2 and from s2 to s1:
static bool UniqueMapping(string s1, string s2)
{
int length = Math.Min(s1.Length, s2.Length);
var dict = new Dictionary<char, char>(length);
for (int i = 0; i < length; i++)
{
char c1 = s1[i];
char c2 = s2[i];
bool contained = dict.TryGetValue(c1, out char c);
if (contained && c2 != c)
{
return false;
}
dict[c1] = c2;
}
return true;
}
Here are your samples. Note that i use UniqueMapping twice(if true after 1st):
static void Main(string[] args)
{
var items = new List<string[]> { new[]{ "aab", "ttd" }, new[] { "tab", "ttd" }, new[] { "ala bala portocala", "cuc dcuc efghficuc" }, new[] { "ala bala portocala", "cuc dcuc efghijcuc" } };
foreach (string[] item in items)
{
bool result = UniqueMapping(item[0], item[1]);
if(result) result = UniqueMapping(item[1], item[0]);
Console.WriteLine($"Word 1 <{item[0]}> Word 2 <{item[1]}> UniqueMapping? {result}");
}
}
.NET Fiddle: https://dotnetfiddle.net/4DtIyH

Find permutation of one string into other string program

Trying to make an program where it just check, if permutation of string s1 exists in string s2 or not.
Created below program and it works for below test case.
Input:
s1 = "ab"
s2 = "eidballl"
Output:
True
Explanation: s2 contains one permutation of s1 (that is ba).
But this get fail when, input s2="sdfdadddbd" , s1="ab", expected as, false, but got true.
I'm trying to figure out what is missing here. Using a sliding window approach. Below my code in c#:
public bool CheckInclusion(string s1, string s2) {
var intCharArray = new int[256];
foreach(char c in s1)
{
intCharArray[c]++;
}
int start=0,end=0;
int count=s1.Length;
bool found=false;
while(end<s2.Length)
{
if (intCharArray[s2[end]]>0) { count--;}
intCharArray[s2[end]]--;
Console.WriteLine("end:" + end + " start:"+ start);
if(end-start==s1.Length) {
if (count==0) {return true;}
if (intCharArray[s2[start]]>=0)
{
count++;
}
intCharArray[s2[start]]++;
start++;
}
end++;
}
return false;
}

you need to check all characters of permutation exist in any range of [i, i + p.Length) of the string
static class StringExtensions
{
public static bool ContainsAnyPermutationOf(this string str, string p)
{
Dictionary<char, int> chars_count = p.CreateChar_CountDictionary();
for (int i = 0; i <= str.Length - p.Length; i++)
{
string subString = str.Substring(i, p.Length);
if (DictionaryMatch(chars_count, subString.CreateChar_CountDictionary()))
{
return true;
}
}
return false;
}
private static bool DictionaryMatch(Dictionary<char, int> dictionary1, Dictionary<char, int> dictionary2)
{
if (dictionary1.Count != dictionary2.Count)
{
return false;
}
foreach (var kvp in dictionary1)
{
if (!dictionary2.ContainsKey(kvp.Key))
{
return false;
}
dictionary2[kvp.Key] = dictionary2[kvp.Key] - 1;
if (dictionary2[kvp.Key] == 0)
{
dictionary2.Remove(kvp.Key);
}
}
return true;
}
private static Dictionary<char, int> CreateChar_CountDictionary(this string str)
{
Dictionary<char, int> dic = new Dictionary<char, int>();
for (int i = 0; i < str.Length; i++)
{
if (!dic.ContainsKey(str[i]))
{
dic.Add(str[i], default);
}
dic[str[i]] = dic[str[i]] + 1;
}
return dic;
}
}
usage:
static void Main(string[] args)
{
Console.WriteLine("sdfdadddbd".ContainsAnyPermutationOf("ab"));
}

I guess the question is similar to LeetCode 567. These are simple, efficient, low-complexity accepted solutions:
C#
class Solution {
public bool CheckInclusion(string s1, string s2) {
int lengthS1 = s1.Length;
int lengthS2 = s2.Length;
if (lengthS1 > lengthS2)
return false;
int[] countmap = new int[26];
for (int i = 0; i < lengthS1; i++)
countmap[s1[i] - 97]++;
int[] bCount = new int[26];
for (int i = 0; i < lengthS2; i++) {
bCount[s2[i] - 97]++;
if (i >= (lengthS1 - 1)) {
if (allZero(countmap, bCount))
return true;
bCount[s2[i - (lengthS1 - 1)] - 97]--;
}
}
return false;
}
private bool allZero(int[] s1, int[] s2) {
for (int i = 0; i < 26; i++) {
if (s1[i] != s2[i])
return false;
}
return true;
}
}
Java
class Solution {
public boolean checkInclusion(String s1, String s2) {
int lengthS1 = s1.length();
int lengthS2 = s2.length();
if (lengthS1 > lengthS2)
return false;
int[] countmap = new int[26];
for (int i = 0; i < lengthS1; i++) {
countmap[s1.charAt(i) - 97]++;
countmap[s2.charAt(i) - 97]--;
}
if (allZero(countmap))
return true;
for (int i = lengthS1; i < lengthS2; i++) {
countmap[s2.charAt(i) - 97]--;
countmap[s2.charAt(i - lengthS1) - 97]++;
if (allZero(countmap))
return true;
}
return false;
}
private boolean allZero(int[] count) {
for (int i = 0; i < 26; i++)
if (count[i] != 0)
return false;
return true;
}
}
Python
class Solution:
def checkInclusion(self, s1, s2):
count_map_s1 = collections.Counter(s1)
count_map_s2 = collections.Counter(s2[:len(s1)])
for i in range(len(s1), len(s2)):
if count_map_s1 == count_map_s2:
return True
count_map_s2[s2[i]] += 1
count_map_s2[s2[i - len(s1)]] -= 1
if count_map_s2[s2[i - len(s1)]] == 0:
del(count_map_s2[s2[i - len(s1)]])
return count_map_s2 == count_map_a
Reference
The codes are explained in the following links:
LeetCode 567 Solution
LeetCode 567 Discussion Board
These two answers are also useful to look into:
Link 1
Link 2

private static bool CheckPermutationInclusion(string s1, string s2)
{
return Enumerable.Range(0, s2.Length - s1.Length)
.Select(i => s2.Substring(i, s1.Length))
.Any(x => x.All(y => s1.Contains(y)));
}
Description:
Enumerable.Range(Int32, Int32) Method: Generates a sequence of integral numbers within a specified range.
Enumerable.Select Method: Projects each element of a sequence into a new form.
Enumerable.All Method: Determines whether all elements of a sequence satisfy a condition.
Enumerable.Any Method: Determines whether any element of a sequence exists or satisfies a condition.
Do not forget using System.Linq;.

Why Is This Code Running Longer Character Combinations Than Necessary?

I'm a math student with little to no experience programming, but I wrote this to act like a brute force algorithm. It seems to run fine except that it runs all the password combinations out to 3 characters for passwords as short as 2. Also I'm sure there's a way to refactor the for and if statements as well. Any help would be appreciated, thanks.
I've already been testing to see if some of the if statements aren't executing, and it looks like the statements with "console.writeln(Is this executing)" aren't executing but I'm not really sure.
public Form1()
{
InitializeComponent();
}
static char[] Match ={'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f','g','h','i','j' ,'k','l','m','n','o','p',
'q','r','s','t','u','v','w','x','y','z','A','B','C','D','E','F','G','H','I','J','C','L','M','N','O','P',
'Q','R','S','T','U','V','X','Y','Z','!','?',' ','*','-','+'};
private string[] tempPass;
private void button1_Click(object sender, EventArgs e)
{
string tempPass1 = "lm";
string result = String.Empty;
int passLength = 1;
int maxLength = 17;
tempPass = new string[passLength];
for (int i = 0; i < Match.Length; i++)
{
if (tempPass1 != result)
{
tempPass[0] = Match[i].ToString();
result = String.Concat(tempPass);
if (passLength > 1)
{
for (int j = 0; j < Match.Length; j++)
{
if (tempPass1 != result)
{
tempPass[1] = Match[j].ToString();
result = String.Concat(tempPass);
if (passLength > 2)
{
for (int k = 0; k < Match.Length; k++)
{
if (tempPass1 != result)
{
tempPass[2] = Match[k].ToString();
result = String.Concat(tempPass);
if (tempPass[0] == "+" && tempPass[1] == "+" && tempPass[2] == "+" && tempPass1 != result)
{
Console.WriteLine("This will execute?");
passLength++;
tempPass = new string[passLength];
k = 0;
j = 0;
i = 0;
}
else if (result == tempPass1)
{
Console.WriteLine("Broken");
Console.WriteLine("This is big gay: " + result);
break;
}
}
}
}
if (tempPass[0] == "+" && tempPass[1] == "+" && tempPass1 != result)
{
Console.WriteLine("Did this execute?");
passLength++;
tempPass = new string[passLength];
j = 0;
i = 0;
}
else if (result == tempPass1)
{
Console.WriteLine("Broken");
Console.WriteLine("This is bigger gay: " + result);
break;
}
}
}
}
//tempPass[1] = "World!";
//Console.WriteLine(result);
if (tempPass[tempPass.Length - 1] == "+" && tempPass1 != result)
{
passLength++;
tempPass = new string[passLength];
Console.WriteLine(tempPass.Length + " " + result + " " + "Success");
Console.WriteLine(i);
i = 0; /**update
j = 0;
k = 0;
l = 0;
m = 0;*/
}
else if (result == tempPass1)
{
Console.WriteLine("Broken");
Console.WriteLine("This is biggest gay: " + result);
}
}
}
}

Play with this; modified from my answer here. It'll show you all the 2 and 3 length combinations. Clicking the button will start/stop the generation process. You need a button, label, and a timer:
public partial class Form1 : Form
{
private Revision rev;
public Form1()
{
InitializeComponent();
rev = new Revision("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!? *-+", "00");
label1.Text = rev.CurrentRevision;
}
private void button1_Click(object sender, EventArgs e)
{
timer1.Enabled = !timer1.Enabled;
}
private void timer1_Tick(object sender, EventArgs e)
{
rev.NextRevision();
if (rev.CurrentRevision.Length == 4)
{
timer1.Stop();
MessageBox.Show("Sequence Complete");
// make it start back at the beginning?
rev = new Revision("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!? *-+", "00");
label1.Text = rev.CurrentRevision;
}
else
{
label1.Text = rev.CurrentRevision;
}
}
}
public class Revision
{
private string chars;
private char[] values;
private System.Text.StringBuilder curRevision;
public Revision()
{
this.DefaultRevision();
}
public Revision(string validChars)
{
if (validChars.Length > 0)
{
chars = validChars;
values = validChars.ToCharArray();
curRevision = new System.Text.StringBuilder(values[0]);
}
else
{
this.DefaultRevision();
}
}
public Revision(string validChars, string startingRevision)
: this(validChars)
{
curRevision = new System.Text.StringBuilder(startingRevision.ToUpper());
int i = 0;
for (i = 0; i <= curRevision.Length - 1; i++)
{
if (Array.IndexOf(values, curRevision[i]) == -1)
{
curRevision = new System.Text.StringBuilder(values[0]);
break;
}
}
}
private void DefaultRevision()
{
chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
values = chars.ToCharArray();
curRevision = new System.Text.StringBuilder(values[0]);
}
public string ValidChars
{
get { return chars; }
}
public string CurrentRevision
{
get { return curRevision.ToString(); }
}
public string NextRevision(int numRevisions = 1)
{
bool forward = (numRevisions > 0);
numRevisions = Math.Abs(numRevisions);
int i = 0;
for (i = 1; i <= numRevisions; i++)
{
if (forward)
{
this.Increment();
}
else
{
this.Decrement();
}
}
return this.CurrentRevision;
}
private void Increment()
{
char curChar = curRevision[curRevision.Length - 1];
int index = Array.IndexOf(values, curChar);
if (index < (chars.Length - 1))
{
index = index + 1;
curRevision[curRevision.Length - 1] = values[index];
}
else
{
curRevision[curRevision.Length - 1] = values[0];
int i = 0;
int startPosition = curRevision.Length - 2;
for (i = startPosition; i >= 0; i += -1)
{
curChar = curRevision[i];
index = Array.IndexOf(values, curChar);
if (index < (values.Length - 1))
{
index = index + 1;
curRevision[i] = values[index];
return;
}
else
{
curRevision[i] = values[0];
}
}
curRevision.Insert(0, values[0]);
}
}
private void Decrement()
{
char curChar = curRevision[curRevision.Length - 1];
int index = Array.IndexOf(values, curChar);
if (index > 0)
{
index = index - 1;
curRevision[curRevision.Length - 1] = values[index];
}
else
{
curRevision[curRevision.Length - 1] = values[values.Length - 1];
int i = 0;
int startPosition = curRevision.Length - 2;
for (i = startPosition; i >= 0; i += -1)
{
curChar = curRevision[i];
index = Array.IndexOf(values, curChar);
if (index > 0)
{
index = index - 1;
curRevision[i] = values[index];
return;
}
else
{
curRevision[i] = values[values.Length - 1];
}
}
curRevision.Remove(0, 1);
if (curRevision.Length == 0)
{
curRevision.Insert(0, values[0]);
}
}
}
}

C# - Check if string contains characters of another string at the same order

I would like to check if a string contains the characters of another string (returning true or false), but it needs to be in the "right" order but not necessarily contiguous.
Example:
String firstWord = "arm";
String secondWord = "arandomword"; //TRUE - ARandoMword
String thirdWord = "road"; //FALSE - ARanDOmword
The word "arandomword" contains the letters of the word "road" but it's not possible to write it, because they are not at the right order.
Anyone, please?

Use regex. Something simple that passes your tests in linqpad:
void Main()
{
String firstWord = "arm";
String secondWord = "arandomword"; //TRUE - ARandoMword
String thirdWord = "road";
Regex.IsMatch(secondWord,makeRegex(firstWord.ToCharArray())).Dump();
}
// Define other methods and classes here
String makeRegex(char[] chars)
{
StringBuilder sb = new StringBuilder();
foreach (var element in chars.Select(c => Regex.Escape(c.ToString()))
.Select(c => c + ".*"))
{
sb.Append(element);
}
return sb.ToString();
}

you could define an extension method like this:
public static class StringExtensions
{
public static bool ContainsWord(this string word, string otherword)
{
int currentIndex = 0;
foreach(var character in otherword)
{
if ((currentIndex = word.IndexOf(character, currentIndex)) == -1)
return false;
}
return true;
}
}
and call it as expressive as:
String firstWord = "arm";
String secondWord = "arandomword"; //TRUE - ARandoMword
String thirdWord = "road"; //FALSE - ARanDOmword
var ret = secondWord.ContainsWord(firstWord); // true
var ret2 = thirdWord.ContainsWord(firstWord); // false

Something like this?
bool HasLettersInOrder(string firstWord, string secondWord)
{
int lastPos = -1;
foreach (char c in firstWord)
{
lastPos++;
while (lastPos < secondWord.Length && secondWord[lastPos] != c)
lastPos++;
if (lastPos == secondWord.Length)
return false;
}
return true;
}

I can not check right now, but something along the lines:
int i = 0, j = 0;
while(i < first.Length && j < second.Length)
{
while(first[i] != second[j] && j < second.Length) j++;
i++;
j++
}
bool b = i == first.Length;

Thanks for all the replies. I've tried and tried and I did it my way. Definitively it's not the shortest way to do it, but at least it's working:
public static Boolean checkWords(String smallerWord, String biggerWord)
{
int position = 0;
bool gotFirst = false;
bool gotAnother = false;
int positionBigger = 0;
String word = "";
for(int positionSmaller = 0; positionSmaller < smallerWord.Length; positionSmaller++)
{
if(!gotFirst)
{
if(biggerWord.Contains(smallerWord[positionSmaller].ToString()))
{
position = biggerWord.IndexOf(smallerWord[positionSmaller].ToString());
gotFirst = true;
word = smallerWord[positionSmaller].ToString();
}
}
else
{
gotAnother = false;
positionBigger = position + 1;
while(!gotAnother)
{
if(positionBigger < biggerWord.Length)
{
if(biggerWord[positionBigger].ToString().Equals(smallerWord[positionSmaller].ToString()))
{
position = positionBigger;
gotAnother = true;
word += smallerWord[positionSmaller].ToString();
}
else
{
positionBigger++;
}
}
else
{
gotAnother = true;
}
}
}
}
if(smallerWord.Equals(word))
{
return true;
}
else
{
return false;
}
}

Finding all positions of substring in a larger string in C#

I have a large string I need to parse, and I need to find all the instances of extract"(me,i-have lots. of]punctuation, and store the index of each to a list.
So say this piece of string was in the beginning and middle of the larger string, both of them would be found, and their indexes would be added to the List. and the List would contain 0 and the other index whatever it would be.
I've been playing around, and the string.IndexOf does almost what I'm looking for, and I've written some code - but it's not working and I've been unable to figure out exactly what is wrong:
List<int> inst = new List<int>();
int index = 0;
while (index < source.LastIndexOf("extract\"(me,i-have lots. of]punctuation", 0) + 39)
{
int src = source.IndexOf("extract\"(me,i-have lots. of]punctuation", index);
inst.Add(src);
index = src + 40;
}
inst = The list
source = The large string
Any better ideas?

Here's an example extension method for it:
public static List<int> AllIndexesOf(this string str, string value) {
if (String.IsNullOrEmpty(value))
throw new ArgumentException("the string to find may not be empty", "value");
List<int> indexes = new List<int>();
for (int index = 0;; index += value.Length) {
index = str.IndexOf(value, index);
if (index == -1)
return indexes;
indexes.Add(index);
}
}
If you put this into a static class and import the namespace with using, it appears as a method on any string, and you can just do:
List<int> indexes = "fooStringfooBar".AllIndexesOf("foo");
For more information on extension methods, http://msdn.microsoft.com/en-us/library/bb383977.aspx
Also the same using an iterator:
public static IEnumerable<int> AllIndexesOf(this string str, string value) {
if (String.IsNullOrEmpty(value))
throw new ArgumentException("the string to find may not be empty", "value");
for (int index = 0;; index += value.Length) {
index = str.IndexOf(value, index);
if (index == -1)
break;
yield return index;
}
}

Why don't you use the built in RegEx class:
public static IEnumerable<int> GetAllIndexes(this string source, string matchString)
{
matchString = Regex.Escape(matchString);
foreach (Match match in Regex.Matches(source, matchString))
{
yield return match.Index;
}
}
If you do need to reuse the expression then compile it and cache it somewhere. Change the matchString param to a Regex matchExpression in another overload for the reuse case.

using LINQ
public static IEnumerable<int> IndexOfAll(this string sourceString, string subString)
{
return Regex.Matches(sourceString, subString).Cast<Match>().Select(m => m.Index);
}

Polished version + case ignoring support:
public static int[] AllIndexesOf(string str, string substr, bool ignoreCase = false)
{
if (string.IsNullOrWhiteSpace(str) ||
string.IsNullOrWhiteSpace(substr))
{
throw new ArgumentException("String or substring is not specified.");
}
var indexes = new List<int>();
int index = 0;
while ((index = str.IndexOf(substr, index, ignoreCase ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal)) != -1)
{
indexes.Add(index++);
}
return indexes.ToArray();
}

It could be done in efficient time complexity using KMP algorithm in O(N + M) where N is the length of text and M is the length of the pattern.
This is the implementation and usage:
static class StringExtensions
{
public static IEnumerable<int> AllIndicesOf(this string text, string pattern)
{
if (string.IsNullOrEmpty(pattern))
{
throw new ArgumentNullException(nameof(pattern));
}
return Kmp(text, pattern);
}
private static IEnumerable<int> Kmp(string text, string pattern)
{
int M = pattern.Length;
int N = text.Length;
int[] lps = LongestPrefixSuffix(pattern);
int i = 0, j = 0;
while (i < N)
{
if (pattern[j] == text[i])
{
j++;
i++;
}
if (j == M)
{
yield return i - j;
j = lps[j - 1];
}
else if (i < N && pattern[j] != text[i])
{
if (j != 0)
{
j = lps[j - 1];
}
else
{
i++;
}
}
}
}
private static int[] LongestPrefixSuffix(string pattern)
{
int[] lps = new int[pattern.Length];
int length = 0;
int i = 1;
while (i < pattern.Length)
{
if (pattern[i] == pattern[length])
{
length++;
lps[i] = length;
i++;
}
else
{
if (length != 0)
{
length = lps[length - 1];
}
else
{
lps[i] = length;
i++;
}
}
}
return lps;
}
and this is an example of how to use it:
static void Main(string[] args)
{
string text = "this is a test";
string pattern = "is";
foreach (var index in text.AllIndicesOf(pattern))
{
Console.WriteLine(index); // 2 5
}
}

Without Regex, using string comparison type:
string search = "123aa456AA789bb9991AACAA";
string pattern = "AA";
Enumerable.Range(0, search.Length)
.Select(index => { return new { Index = index, Length = (index + pattern.Length) > search.Length ? search.Length - index : pattern.Length }; })
.Where(searchbit => searchbit.Length == pattern.Length && pattern.Equals(search.Substring(searchbit.Index, searchbit.Length),StringComparison.OrdinalIgnoreCase))
.Select(searchbit => searchbit.Index)
This returns {3,8,19,22}. Empty pattern would match all positions.
For multiple patterns:
string search = "123aa456AA789bb9991AACAA";
string[] patterns = new string[] { "aa", "99" };
patterns.SelectMany(pattern => Enumerable.Range(0, search.Length)
.Select(index => { return new { Index = index, Length = (index + pattern.Length) > search.Length ? search.Length - index : pattern.Length }; })
.Where(searchbit => searchbit.Length == pattern.Length && pattern.Equals(search.Substring(searchbit.Index, searchbit.Length), StringComparison.OrdinalIgnoreCase))
.Select(searchbit => searchbit.Index))
This returns {3, 8, 19, 22, 15, 16}

I noticed that at least two proposed solutions don't handle overlapping search hits. I didn't check the one marked with the green checkmark. Here is one that handles overlapping search hits:
public static List<int> GetPositions(this string source, string searchString)
{
List<int> ret = new List<int>();
int len = searchString.Length;
int start = -1;
while (true)
{
start = source.IndexOf(searchString, start +1);
if (start == -1)
{
break;
}
else
{
ret.Add(start);
}
}
return ret;
}

public List<int> GetPositions(string source, string searchString)
{
List<int> ret = new List<int>();
int len = searchString.Length;
int start = -len;
while (true)
{
start = source.IndexOf(searchString, start + len);
if (start == -1)
{
break;
}
else
{
ret.Add(start);
}
}
return ret;
}
Call it like this:
List<int> list = GetPositions("bob is a chowder head bob bob sldfjl", "bob");
// list will contain 0, 22, 26

Hi nice answer by #Matti Virkkunen
public static List<int> AllIndexesOf(this string str, string value) {
if (String.IsNullOrEmpty(value))
throw new ArgumentException("the string to find may not be empty", "value");
List<int> indexes = new List<int>();
for (int index = 0;; index += value.Length) {
index = str.IndexOf(value, index);
if (index == -1)
return indexes;
indexes.Add(index);
index--;
}
}
But this covers tests cases like AOOAOOA
where substring
are AOOA and AOOA
Output 0 and 3

#csam is correct in theory, although his code will not complie and can be refractored to
public static IEnumerable<int> IndexOfAll(this string sourceString, string matchString)
{
matchString = Regex.Escape(matchString);
return from Match match in Regex.Matches(sourceString, matchString) select match.Index;
}

public static Dictionary<string, IEnumerable<int>> GetWordsPositions(this string input, string[] Susbtrings)
{
Dictionary<string, IEnumerable<int>> WordsPositions = new Dictionary<string, IEnumerable<int>>();
IEnumerable<int> IndexOfAll = null;
foreach (string st in Susbtrings)
{
IndexOfAll = Regex.Matches(input, st).Cast<Match>().Select(m => m.Index);
WordsPositions.Add(st, IndexOfAll);
}
return WordsPositions;
}

Based on the code I've used for finding multiple instances of a string within a larger string, your code would look like:
List<int> inst = new List<int>();
int index = 0;
while (index >=0)
{
index = source.IndexOf("extract\"(me,i-have lots. of]punctuation", index);
inst.Add(index);
index++;
}

I found this example and incorporated it into a function:
public static int solution1(int A, int B)
{
// Check if A and B are in [0...999,999,999]
if ( (A >= 0 && A <= 999999999) && (B >= 0 && B <= 999999999))
{
if (A == 0 && B == 0)
{
return 0;
}
// Make sure A < B
if (A < B)
{
// Convert A and B to strings
string a = A.ToString();
string b = B.ToString();
int index = 0;
// See if A is a substring of B
if (b.Contains(a))
{
// Find index where A is
if (b.IndexOf(a) != -1)
{
while ((index = b.IndexOf(a, index)) != -1)
{
Console.WriteLine(A + " found at position " + index);
index++;
}
Console.ReadLine();
return b.IndexOf(a);
}
else
return -1;
}
else
{
Console.WriteLine(A + " is not in " + B + ".");
Console.ReadLine();
return -1;
}
}
else
{
Console.WriteLine(A + " must be less than " + B + ".");
// Console.ReadLine();
return -1;
}
}
else
{
Console.WriteLine("A or B is out of range.");
//Console.ReadLine();
return -1;
}
}
static void Main(string[] args)
{
int A = 53, B = 1953786;
int C = 78, D = 195378678;
int E = 57, F = 153786;
solution1(A, B);
solution1(C, D);
solution1(E, F);
Console.WriteLine();
}
Returns:
53 found at position 2
78 found at position 4
78 found at position 7
57 is not in 153786

How is this alternative implementation?
public static class MyExtensions
{
public static int HowMany(this string str, char needle)
{
int counter = 0;
int nextIndex = 0;
for (; nextIndex != -1; )
{
nextIndex = str.IndexOf(needle, nextIndex);
if (nextIndex != -1)
{
counter++;
//step over to the next char
nextIndex++;
}
}
return counter;
}
}

you can use linq to select and enumerate all elements, then find by any string:
I've created a class:
class Pontos
{
//index on string
public int Pos { get; set; }
//caractere
public string Caractere { get; set; }
}
And use like this:
int count = 0;
var pontos = texto.Select(y => new Pontos { Pos = count++, Caractere = y.ToString() }).Where(x=>x.Caractere == ".").ToList();
then:
input string:
output list:
PS: SeForNumero is another field of my class, I need this for my own purposes, but is not necessary to this use.