I want to remove the repeating items of a list.I can realize it whit Distinct() easily.But i also need to get the order number of the items which have been removed.I can't find any function in linq to solve the problem and finally realize it with the following code:
public List<string> Repeat(List<string> str)
{
var Dlist = str.Distinct();
List<string> repeat = new List<string>();
foreach (string aa in Dlist)
{
int num = 0;
string re = "";
for (int i = 1; i <= str.LongCount(); i++)
{
if (aa == str[i - 1])
{
num = num + 1;
re = re + " - " + i;
}
}
if (num > 1)
{
repeat.Add(re.Substring(3));
}
}
return repeat;
}
Is there any other way to solve the problem more simple? Or is there any function in linq I missed?Any advice will be appreciated.
This query does exactly the same as your function, if I'm not mistaken:
var repeated = str.GroupBy(s => s).Where(group => group.Any())
.Select(group =>
{
var indices = Enumerable.Range(1, str.Count).Where(i => str[i-1] == group.Key).ToList();
return string.Join(" - ", group.Select((s, i) => indices[i]));
});
It firstly groups the items of the original list, so that every item with the same content is in a group. Then it searches for all indices of the items in the group in the original list, so that we have all the indices of the original items of the group. Then it joins the indices to a string, so that the resulting format is similiar to the one you requested. You could also transform this statement lambda to an anonymous lambda:
var repeated = str.GroupBy(s => s).Where(group => group.Any())
.Select(group => string.Join(" - ",
group.Select((s, i) =>
Enumerable.Range(1, str.Count).Where(i2 => str[i2 - 1] == group.Key).ToList()[i])));
However, this significantly reduces performance.
I tested this with the following code:
public static void Main()
{
var str = new List<string>
{
"bla",
"bla",
"baum",
"baum",
"nudel",
"baum",
};
var copy = new List<string>(str);
var repeated = str.GroupBy(s => s).Where(group => group.Any())
.Select(group => string.Join(" - ",
group.Select((s, i) =>
Enumerable.Range(1, str.Count).Where(i2 => str[i2 - 1] == group.Key).ToList()[i])));
var repeated2 = Repeat(str);
var repeated3 = str.GroupBy(s => s).Where(group => group.Any())
.Select(group =>
{
var indices = Enumerable.Range(1, str.Count).Where(i => str[i-1] == group.Key).ToList();
return string.Join(" - ", group.Select((s, i) => indices[i]));
});
Console.WriteLine(string.Join("\n", repeated) + "\n");
Console.WriteLine(string.Join("\n", repeated2) + "\n");
Console.WriteLine(string.Join("\n", repeated3));
Console.ReadLine();
}
public static List<string> Repeat(List<string> str)
{
var distinctItems = str.Distinct();
var repeat = new List<string>();
foreach (var item in distinctItems)
{
var added = false;
var reItem = "";
for (var index = 0; index < str.LongCount(); index++)
{
if (item != str[index])
continue;
added = true;
reItem += " - " + (index + 1);
}
if (added)
repeat.Add(reItem.Substring(3));
}
return repeat;
}
Which has the followin output:
1 - 2
3 - 4 - 6
5
1 - 2
3 - 4 - 6
5
1 - 2
3 - 4 - 6
5
Inside your repeat method you can use following way to get repeated items
var repeated = str.GroupBy(s=>s)
.Where(grp=>grp.Count()>1)
.Select(y=>y.Key)
.ToList();
If I have a string array like this:
string[] str = new string[]{"abc", "bacd", "pacds"};
Then I need output like below using LINQ:
output: abc, abcd, acdps
This should be what you want:
string[] str = new string[] { "abc", "bacd", "pacds" };
var result = str.Select(c => String.Concat(c.OrderBy(d => d)));
The result is IEnumerable<string> but if you want the result in an string array add .ToArray():
var result = str.Select(c => String.Concat(c.OrderBy(d => d))).ToArray();
The result:
You can use String.Concat(st.OrderBy(c => c)) to order string by its characters.
str.ToList().ForEach((val) => {
val = String.Concat(val.OrderBy(c => c));
});
str.Select(x => x.ToCharArray().OrderBy(c => c).Aggregate("", (s,c)=>s+c))
this just to change the array strings into chars-ordered ones
static void orderChars(string[] str)
{
for (int i = 0; i < str.Length; i++)
str[i] = new string(str[i].OrderBy(c => c).ToArray());
}
As bassfader commented , show your code and say where u stuck , then we can guide you, anyway ..
You can write it like this ,
string[] a = new string[]
{"Indonesian","Korean","Japanese","English","German"};
var sort = from s in a orderby s select s;
I want to find the duplicates for a given string, I tried for collections, It is working fine, but i don't know how to do it for a string.
Here is the code I tried for collections,
string name = "this is a a program program";
string[] arr = name.Split(' ');
var myList = new List<string>();
var duplicates = new List<string>();
foreach(string res in arr)
{
if (!myList.Contains(res))
{
myList.Add(res);
}
else
{
duplicates.Add(res);
}
}
foreach(string result in duplicates)
{
Console.WriteLine(result);
}
Console.ReadLine();
But I want to find the duplicates for the below string and to store it in an array. How to do that?
eg:- string aa = "elements";
In the above string i want to find the duplicate characters and store it in an array
Can anyone help me?
Linq solution:
string name = "this is a a program program";
String[] result = name.Split(' ')
.GroupBy(word => word)
.Where(chunk => chunk.Count() > 1)
.Select(chunk => chunk.Key)
.ToArray();
Console.Write(String.Join(Environment.NewLine, result));
The same princicple for duplicate characters within a string:
String source = "elements";
Char[] result = source
.GroupBy(c => c)
.Where(chunk => chunk.Count() > 1)
.Select(chunk => chunk.Key)
.ToArray();
// result = ['e']
Console.Write(String.Join(Environment.NewLine, result));
string name = "elements";
var myList = new List<char>();
var duplicates = new List<char>();
foreach (char res in name)
{
if (!myList.Contains(res))
{
myList.Add(res);
}
else if (!duplicates.Contains(res))
{
duplicates.Add(res);
}
}
foreach (char result in duplicates)
{
Console.WriteLine(result);
}
Console.ReadLine();
string is an array of chars. So, you can use your collection approach.
But, I would reccomend typed HashSet. Just load it with string and you'll get array of chars without duplicates, with preserved order.
take a look:
string s = "aaabbcdaaee";
HashSet<char> hash = new HashSet<char>(s);
HashSet<char> hashDup = new HashSet<char>();
foreach (var c in s)
if (hash.Contains(c))
hash.Remove(c);
else
hashDup.Add(c);
foreach (var x in hashDup)
Console.WriteLine(x);
Console.ReadKey();
Instead of a List<> i'd use a HashSet<> because it doesn't allow duplicates and Add returns false in that case. It's more efficient. I'd also use a Dictionary<TKey,Tvalue> instead of the list to track the count of each char:
string text = "elements";
var duplicates = new HashSet<char>();
var duplicateCounts = new Dictionary<char, int>();
foreach (char c in text)
{
int charCount = 0;
bool isDuplicate = duplicateCounts.TryGetValue(c, out charCount);
duplicateCounts[c] = ++charCount;
if (isDuplicate)
duplicates.Add(c);
}
Now you have all unique duplicate chars in the HashSet and the count of each unique char in the dictionary. In this example the set only contains e because it's three times in the string.
So you could output it in the following way:
foreach(char dup in duplicates)
Console.WriteLine("Duplicate char {0} appears {1} times in the text."
, dup
, duplicateCounts[dup]);
For what it's worth, here's a LINQ one-liner which also creates a Dictionary that only contains the duplicate chars and their count:
Dictionary<char, int> duplicateCounts = text
.GroupBy(c => c)
.Where(g => g.Count() > 1)
.ToDictionary(g => g.Key, g => g.Count());
I've shown it as second approach because you should first understand the standard way.
string name = "this is a a program program";
var arr = name.Split(' ').ToArray();
var dup = arr.Where(p => arr.Count(q => q == p) > 1).Select(p => p);
HashSet<string> hash = new HashSet<string>(dup);
string duplicate = string.Join(" ", hash);
You can do this through `LINQ
string name = "this is a a program program";
var d = name.Split(' ').GroupBy(x => x).Select(y => new { word = y.Key, Wordcount = y.Count() }).Where(z=>z.cou > 1).ToList();
Use LINQ to group values:
public static IEnumerable<T> GetDuplicates<T>(this IEnumerable<T> list)
{
return list.GroupBy(item => item).SelectMany(group => group.Skip(1));
}
public static bool HasDuplicates<T>(this IEnumerable<T> list)
{
return list.GetDuplicates().IsNotEmpty();
}
Then you use these extensions like this:
var list = new List<string> { "a", "b", "b", "c" };
var duplicatedValues = list.GetDuplicates();
I want to count how many numbers (only 0,1,2,3) and letters (a,b,c,d) were used in a line that I'm checking - they are mixed, for example: 3b1c1c1a1a0b1a1d3d0a3c. How can I count that?
int numbers = 0;
int letters = 0;
foreach(char a in myString)
{
if (Char.IsDigit(a))
numbers ++;
else if (Char.IsLetter(a)){
letters ++;
}
You could also use predefined Linq expressions if these need to be re-used:
var characterList = "234234abce".ToCharArray();
var validCharacters = "0123abcd".ToCharArray();
Func<char, bool> ValidLetter = delegate(char c){
return Char.IsLetter(c) && validCharacters.Contains(c);
};
Func<char, bool> ValidNumber = delegate(char c){
return Char.IsDigit(c) && validCharacters.Contains(c);
};
var letterCount = characterList.Where(c => ValidLetter(c)).Count();
var numberCount = characterList.Where(c => ValidNumber(c)).Count();
You can use the ASCII code to get it work
for(int i = 0 ; i < str.Length ; i++){
int asciicode = (int)str[i];
if(asciicode >= 48 && asciicode <= 57)
number++;
else
alphabet++;
}
This is an example to find the count of character "1":
string input = "3b1c1c1a1a0b1a1d3d0a3c";
int count = input.ToArray().Count(i => i == '1');
There's a method for doing that:
int count = myString.ToCharArray().Where(c => Char.IsLetterOrDigit(c)).Count();
If you want to split them out then:
int letterCount = myString.ToCharArray().Where(c => Char.IsLetter(c)).Count();
int numberCount = myString.ToCharArray().Where(c => Char.IsDigit(c)).Count();
If you want to filter them based on the numbers:
List<char> searchFor = new List<char>() { '0', '1', '2', '3' };
int numberCount = myString.ToCharArray().Where(c => searchFor.Contains(c)).Count();
Below meets your requirements:
string acceptedChars = "0123abcd";
var res = "3b1c1c1a1a0b1a1d3d0a3c".ToCharArray()
.Where(x => acceptedChars.Contains(x))
.GroupBy(x => char.IsDigit(x))
.Select(g => new{ isDigit = g.Key, count = g.Count() } );
var digitsCount = res.Single(r => r.isDigit == true).count;
var lettersCount = res.Single(r => r.isDigit == false).count;
I have a linq query that does something simple like:
var k = people.Select(x=>new{x.ID, x.Name});
I then want a function or linq lambda, or something that will output the names in sentence format using commas and "ands".
{1, John}
{2, Mark}
{3, George}
to
"1:John, 2:Mark and 3:George"
I'm fine with hardcoding the ID + ":" + Name part, but it could be a ToString() depending on the type of the linq query result. I'm just wondering if there is a neat way to do this with linq or String.Format().
public string ToPrettyCommas<T>(
List<T> source,
Func<T, string> stringSelector
)
{
int count = source.Count;
Func<int, string> prefixSelector = x =>
x == 0 ? "" :
x == count - 1 ? " and " :
", ";
StringBuilder sb = new StringBuilder();
for(int i = 0; i < count; i++)
{
sb.Append(prefixSelector(i));
sb.Append(stringSelector(source[i]));
}
string result = sb.ToString();
return result;
}
Called with:
string result = ToPrettyCommas(people, p => p.ID.ToString() + ":" + p.Name);
Why Linq?
StringBuilder sb = new StringBuilder();
for(int i=0;i<k.Count();i++)
{
sb.Append(String.Format("{0}:{1}", k[i].ID, k[i].Name);
if(i + 2 < k.Count())
sb.Append(", ");
else if(i + 1 < k.Count())
sb.Append(" and ");
}
Really, all Linq will let you do is hide the loop.
Also, make sure you do or do not want the "Oxford Comma"; this algorithm will not insert one, but a small change will (append the comma and space after every element except the last, and also append "and " after the next-to-last).
Just for fun, here’s something that really uses functional LINQ — no loop and no StringBuilder. Of course, it’s pretty slow.
var list = new[] { new { ID = 1, Name = "John" },
new { ID = 2, Name = "Mark" },
new { ID = 3, Name = "George" } };
var resultAggr = list
.Select(item => item.ID + ":" + item.Name)
.Aggregate(new { Sofar = "", Next = (string) null },
(agg, next) => new { Sofar = agg.Next == null ? "" :
agg.Sofar == "" ? agg.Next :
agg.Sofar + ", " + agg.Next,
Next = next });
var result = resultAggr.Sofar == "" ? resultAggr.Next :
resultAggr.Sofar + " and " + resultAggr.Next;
// Prints 1:John, 2:Mark and 3:George
Console.WriteLine(result);
Much like the rest, this isn't better than using a string builder, but you can go (ignoring the ID, you can add it in):
IEnumerable<string> names = new[] { "Tom", "Dick", "Harry", "Abe", "Bill" };
int count = names.Count();
string s = String.Join(", ", names.Take(count - 2)
.Concat(new [] {String.Join(" and ", names.Skip(count - 2))}));
This approach pretty much abuses Skip and Take's ability to take negative numbers, and String.Join's willingness to take a single parameter, so it works for one, two or more strings.
Using the Select operation that gives you an index, this can be written as a ONE LINE extension method:
public static string ToAndList<T>(this IEnumerable<T> list, Func<T, string> formatter)
{
return string.Join(" ", list.Select((x, i) => formatter(x) + (i < list.Count() - 2 ? ", " : (i < list.Count() - 1 ? " and" : ""))));
}
e.g.
var list = new[] { new { ID = 1, Name = "John" },
new { ID = 2, Name = "Mark" },
new { ID = 3, Name = "George" } }.ToList();
Console.WriteLine(list.ToAndList(x => (x.ID + ": " + x.Name)));
Improving(hopefully) on KeithS's answer:
string nextBit = "";
var sb = new StringBuilder();
foreach(Person person in list)
{
sb.Append(nextBit);
sb.Append(", ");
nextBit = String.Format("{0}:{1}", person.ID, person.Name);
}
sb.Remove(sb.Length - 3, 2);
sb.Append(" and ");
sb.Append(nextBit);
This is not pretty but will do the job using LINQ
string s = string.Join(",", k.TakeWhile(X => X != k.Last()).Select(X => X.Id + ":" + X.Name).ToArray()).TrimEnd(",".ToCharArray()) + " And " + k.Last().Id + ":" + k.Last().Name;
Y'all are making it too complicated:
var list = k.Select(x => x.ID + ":" + x.Name).ToList();
var str = list.LastOrDefault();
str = (list.Count >= 2 ? list[list.Count - 2] + " and " : null) + str;
str = string.Join(", ", list.Take(list.Count - 2).Concat(new[]{str}));
How about this?
var k = people.Select(x=>new{x.ID, x.Name});
var stringified = people
.Select(x => string.Format("{0} : {1}", x.ID, x.Name))
.ToList();
return string.Join(", ", stringified.Take(stringified.Count-1).ToArray())
+ " and " + stringified.Last();
I have refined my previous answer and I believe this is the most elegant solution yet.
However it would only work on reference types that don't repeat in the collection (or else we'd have to use different means for finding out if item is first/last).
Enjoy!
var firstGuy = guys.First();
var lastGuy = guys.Last();
var getSeparator = (Func<Guy, string>)
(guy => {
if (guy == firstGuy) return "";
if (guy == lastGuy) return " and ";
return ", ";
});
var formatGuy = (Func<Guy, string>)
(g => string.Format("{0}:{1}", g.Id, g.Name));
// 1:John, 2:Mark and 3:George
var summary = guys.Aggregate("",
(sum, guy) => sum + getSeparator(guy) + formatGuy(guy));
This can be the way you can achieve your goal
var list = new[] { new { ID = 1, Name = "John" },
new { ID = 2, Name = "Mark" },
new { ID = 3, Name = "George" }
}.ToList();
int i = 0;
string str = string.Empty;
var k = list.Select(x => x.ID.ToString() + ":" + x.Name + ", ").ToList();
k.ForEach(a => { if (i < k.Count() - 1) { str = str + a; } else { str = str.Substring(0, str.Length -2) + " and " + a.Replace("," , ""); } i++; });
Here's a method that doesn't use LINQ, but is probably as efficient as you can get:
public static string Join<T>(this IEnumerable<T> list,
string joiner,
string lastJoiner = null)
{
StringBuilder sb = new StringBuilder();
string sep = null, lastItem = null;
foreach (T item in list)
{
if (lastItem != null)
{
sb.Append(sep);
sb.Append(lastItem);
sep = joiner;
}
lastItem = item.ToString();
}
if (lastItem != null)
{
if (sep != null)
sb.Append(lastJoiner ?? joiner);
sb.Append(lastItem);
}
return sb.ToString();
}
Console.WriteLine(people.Select(x => x.ID + ":" + x.Name).Join(", ", " and "));
Since it never creates a list, looks at an element twice, or appends extra stuff to the StringBuilder, I don't think you can get more efficient. It also works for 0, 1, and 2 elements in the list (as well as more, obviously).
StringBuilder Approach
Here's an Aggregate with a StringBuilder. There's some position determinations that are made to clean up the string and insert the "and" but it's all done at the StringBuilder level.
var people = new[]
{
new { Id = 1, Name = "John" },
new { Id = 2, Name = "Mark" },
new { Id = 3, Name = "George" }
};
var sb = people.Aggregate(new StringBuilder(),
(s, p) => s.AppendFormat("{0}:{1}, ", p.Id, p.Name));
sb.Remove(sb.Length - 2, 2); // remove the trailing comma and space
var last = people.Last();
// index to last comma (-2 accounts for ":" and space prior to last name)
int indexComma = sb.Length - last.Id.ToString().Length - last.Name.Length - 2;
sb.Remove(indexComma - 1, 1); // remove last comma between last 2 names
sb.Insert(indexComma, "and ");
// 1:John, 2:Mark and 3:George
Console.WriteLine(sb.ToString());
A String.Join approach could have been used instead but the "and" insertion and comma removal would generate ~2 new strings.
Regex Approach
Here's another approach using regex that is quite understandable (nothing too cryptic).
var people = new[]
{
new { Id = 1, Name = "John" },
new { Id = 2, Name = "Mark" },
new { Id = 3, Name = "George" }
};
var joined = String.Join(", ", people.Select(p => p.Id + ":" + p.Name).ToArray());
Regex rx = new Regex(", ", RegexOptions.RightToLeft);
string result = rx.Replace(joined, " and ", 1); // make 1 replacement only
Console.WriteLine(result);
The pattern is simply ", ". The magic lies in the RegexOptions.RightToLeft which makes the match occur from the right and thereby makes the replacement occur at the last comma occurrence. There is no static Regex method that accepts the number of replacements with the RegexOptions, hence the instance usage.
Here's one using a slightly modified version of my answer to Eric Lippert's Challenge which is IMHO the most concise with easy to follow logic (if you're familiar with LINQ).
static string CommaQuibblingMod<T>(IEnumerable<T> items)
{
int count = items.Count();
var quibbled = items.Select((Item, index) => new { Item, Group = (count - index - 2) > 0})
.GroupBy(item => item.Group, item => item.Item)
.Select(g => g.Key
? String.Join(", ", g)
: String.Join(" and ", g));
return String.Join(", ", quibbled); //removed braces
}
//usage
var items = k.Select(item => String.Format("{0}:{1}", item.ID, item.Name));
string formatted = CommaQuibblingMod(items);
static public void Linq1()
{
var k = new[] { new[] { "1", "John" }, new[] { "2", "Mark" }, new[] { "3", "George" } };
Func<string[], string> showPerson = p => p[0] + ": " + p[1];
var res = k.Skip(1).Aggregate(new StringBuilder(showPerson(k.First())),
(acc, next) => acc.Append(next == k.Last() ? " and " : ", ").Append(showPerson(next)));
Console.WriteLine(res);
}
could be optimized by moving k.Last() computation to before the loop
public static string ToListingCommaFormat(this List<string> stringList)
{
switch(stringList.Count)
{
case 0:
return "";
case 1:
return stringList[0];
case 2:
return stringList[0] + " and " + stringList[1];
default:
return String.Join(", ", stringList.GetRange(0, stringList.Count-1))
+ ", and " + stringList[stringList.Count - 1];
}
}
This is the method is faster than the 'efficient' Join method posted by Gabe. For one and two items, it is many times faster, and for 5-6 strings, it is about 10% faster. There is no dependency on LINQ. String.Join is faster than StringBuilder for small arrays, which are typical for human-readable text. In grammar, these are called listing commas, and the last comma should always be included to avoid ambiguity. Here is the resulting code:
people.Select(x=> x.ID.ToString() + ":" + x.Name).ToList().ToListingCommaFormat();
There are ways to optimize this since it isn't very efficient, but something like this may work:
var k = people.Select(x => new {x.ID, x.Name}).ToList();
var last = k.Last();
k.Aggregate(new StringBuilder(), (sentence, item) => {
if (sentence.Length > 0)
{
if (item == last)
sentence.Append(" and ");
else
sentence.Append(", ");
}
sentence.Append(item.ID).Append(":").Append(item.Name);
return sentence;
});