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Checking what type of character the unicode character is

I am running through CodeEasy.net's c# program and I have stumbled across a problem I am struggling with. I don't understand why this does not pass.
Write a program that reads from the console one char using
Console.Read() and Convert.ToChar(...) methods. After this, the
program should output "Digit" "Letter" or "Not a digit and not a
letter" to the screen, depending on what the character is.
I have tried int charCode = int.Parse(Console.ReadLine()); as well instead of int charCode = Console.Read(); but nothing seems to work. It keeps giving me the first "if" and last "else" result, but only one of these should print so it is very confusing.
Here is my code so far:
int charCode = Console.Read();
char theRealChar = Convert.ToChar(charCode);
if (char.IsDigit(theRealChar))
{
Console.WriteLine("Digit");
}
if (char.IsLetter(theRealChar))
{
Console.WriteLine("Letter");
}
else
{
Console.WriteLine("Not a digit and not a letter");
}
Any help in making me understand this is much appreciated!

Your else statement is only associated with the second if statement. You've effectively got:
if (firstCondition)
{
// Stuff
}
// You could have unrelated code here
if (secondCondition)
{
// Stuff
}
else
{
// This will execute any time secondCondition isn't true, regardless of firstCondition
}
If you only want it to execute if neither of the earlier if statements, you need the second one to be else if:
if (char.IsDigit(theRealChar))
{
Console.WriteLine("Digit");
}
// Only check this if the first condition isn't met
else if (char.IsLetter(theRealChar))
{
Console.WriteLine("Letter");
}
// Only execute this at all if neither of the above conditions is met
else
{
Console.WriteLine("Not a digit and not a letter");
}

Seems to work fine once you add a missing else before the second if block.
if (char.IsDigit(theRealChar))
{
Console.WriteLine("Digit");
}
else if (char.IsLetter(theRealChar))
{
Console.WriteLine("Letter");
}
else
{
Console.WriteLine("Not a digit and not a letter");
}

c# loop until Console.ReadLine = 'y' or 'n'

I'm fairly new to c#, and writing a simple console app as practice. I want the application to ask a question, and only progress to the next piece of code when the user input equals 'y' or 'n'. Here's what I have so far.
static void Main(string[] args)
{
string userInput;
do
{
Console.WriteLine("Type something: ");
userInput = Console.ReadLine();
} while (string.IsNullOrEmpty(userInput));
Console.WriteLine("You typed " + userInput);
Console.ReadLine();
string wantCount;
do
{
Console.WriteLine("Do you want me to count the characters present? Yes (y) or No (n): ");
wantCount = Console.ReadLine();
string wantCountLower = wantCount.ToLower();
} while ((wantCountLower != 'y') || (wantCountLower != 'n'));
}
I'm having trouble from string wantCount; onwards. What I want to do is ask the user if they want to count the characters in their string, and loop that question until either 'y' or 'n' (without quotes) is entered.
Note that I also want to cater for upper/lower case being entered, so I image I want to convert the wantCount string to lower - I know that how I currently have this will not work as I'm setting string wantCountLower inside the loop, so I cant then reference outside the loop in the while clause.
Can you help me understand how I can go about achieving this logic?

You could move the input check to inside the loop and utilise a break to exit. Note that the logic you've used will always evaluate to true so I've inverted the condition as well as changed your char comparison to a string.
string wantCount;
do
{
Console.WriteLine("Do you want me to count the characters present? Yes (y) or No (n): ");
wantCount = Console.ReadLine();
var wantCountLower = wantCount?.ToLower();
if ((wantCountLower == "y") || (wantCountLower == "n"))
break;
} while (true);
Also note the null-conditional operator (?.) before ToLower(). This will ensure that a NullReferenceException doesn't get thrown if nothing is entered.

If you want to compare a character, then their is not need for ReadLine you can use ReadKey for that, if your condition is this :while ((wantCountLower != 'y') || (wantCountLower != 'n')); your loop will be an infinite one, so you can use && instead for || here or it will be while(wantCount!= 'n') so that it will loops until you press n
char charYesOrNo;
do
{
charYesOrNo = Console.ReadKey().KeyChar;
// do your stuff here
}while(char.ToLower(charYesOrNo) != 'n');

Why do these errors appear? c# - hangman game

I'm fairly new to coding (especially c#) - this is an assignment for a programming fundamentals class - I'm not looking for the answer - I'm looking for someone to explain why I get these two 'error's for a boolean method I'm supposed to create to check if the user's guess for a letter or the full word in a game of hangman.
The errors I get are - 'Unreachable Code detected - for the idx++ part - which doesn't make sense as I've used it in other separate methods..
And Program.CheckGuess(char[], char[], char[], string: not all code paths return a value.
I know I'm not fully finished the aspect. It's probably staring at me in the face - just looking for some guidance. Thanks.
static bool CheckGuess(char[] secrets, char[] mask, char[] letters, string guess)
{
int misses = 0; bool condition = false;
for (int idx = 0; idx < secret.Length; idx++)
{
guess.ToCharArray();
if (mask[idx] == guess[idx])
{
//reveal character or word
condition = true;
}
else
{
misses = misses + 1;
condition = false;
}
return condition;
}
}

You should understand that a return statement, when executed, makes the control jump out of the method and back to the caller.
In your code, your return is statement is placed inside the for loop. When an iteration of the for loop is executed, the control jumps out of the method immediately and goes back to the caller of the method.
As you know, the last part in a for loop header (idx++) is executed when an iteration has finished executing. However, in your case, an iteration will never finish because it just jumps back to the caller when control reaches return. This is why the first error occurred.
You should also understand that every method which doesn't have void as the return type needs to return no matter what.
So what if the for loop's condition (the middle part) is never true? The for loop will never be executed, right? If the for loop isn't executed, then what should the method return?
The error says that not all code path returns a value because the method would not return if the for loop isn't executed.
To fix this, you just need to move the return statement out of the for loop:
static bool CheckGuess(char[] secrets, char[] mask, char[] letters, string guess)
{
int misses = 0; bool condition = false;
for (int idx = 0; idx < secret.Length; idx++)
{
guess.ToCharArray();
if (mask[idx] == guess[idx])
{
//reveal character or word
condition = true;
}
else
{
misses = misses + 1;
condition = false;
}
}
return condition;
}

Because you have a return statement.
When this return inside your for loop is reached, the program jumps out of the loop and thus makes you i++ unreachable.

Reducing time complexity of the code

I have the following code but it takes 20sec to process the 52957 inputs of type BigInteger. This is the question that i want to solve https://www.hackerearth.com/problem/algorithm/girlfriends-demands/
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Numerics;
namespace girldfriends_demands
{
class Program
{
private static string inputString = String.Empty;
private static int testCases=0;
private static BigInteger[,] indexArray;
static void Main(string[] args)
{
initialize();
printDemand();
Console.ReadLine();
}
private static void initialize()
{
inputString = Console.ReadLine();
testCases = int.Parse(Console.ReadLine());
indexArray = new BigInteger[testCases, 2];
for (int i = 0; i < testCases; i++)
{
string[] tokens = Console.ReadLine().Split();
indexArray[i, 0] = BigInteger.Parse(tokens[0]);
indexArray[i, 1] = BigInteger.Parse(tokens[1]);
}
}
private static void printDemand()
{
char[] convertedString = inputString.ToCharArray();
for (int i = 0; i < testCases; i++)
{
BigInteger length=inputString.Length;
BigInteger startf, endf; ;
BigInteger.DivRem(indexArray[i, 0] - 1,length,out startf);
BigInteger.DivRem(indexArray[i, 1]-1,length,out endf);
char c=convertedString[((int)startf)];
char e=convertedString[((int)endf)];
if(c==e)
{
Console.WriteLine("Yes");
}
else
{
Console.WriteLine("No");
}
}
}
}
}
Please specify how to reduce the time complexity of the code.This program gets the letters at the specified position in a string and prints true if they are same else false. Also computing the range at prior to the loop isn't helping

Why you use BigInteger ?
In any case string.length is typeof int.
It mean that if your string exceed 2147483647 (2^31 -1) your program will be broken.
I think changing BigInteger to int will help.

Console.ReadLine().Split()
is the biggest of your problems. For every single line in the file, you create an array of strings, one letter per string. This is a huge performance drain, and almost certainly not what you intended - in particular, it would be wholy unnecessary to use BigInteger to store a single-digit number...
I assume that you actually want to split the line in two based on some delimiter. For example, if your numbers are separated by a comma, you can use
Console.ReadLine().Split(',')
Even then, there is little reason to use BigInteger at all. The operation you're trying to perform is distinctly string-based, and very easy to do with strings. However, I can't really help you more specifically, because your problem description is incredibly ambiguous for such a simple task, and the code is so obviously wrong it's entirely useless to guess at what exactly you're trying to do.
EDIT:
Okay, your link confirmed my assumptions - you are massively overcomplicating this. For example, code like this will do:
var word = Console.ReadLine();
var items = int.Parse(Console.ReadLine());
for (var _ = 0; _ < items; _++)
{
var indices =
Console.ReadLine()
.Split(' ')
.Select(i => (int)((long.Parse(i) - 1) % word.Length))
.ToArray();
Console.WriteLine(word[indices[0]] == word[indices[1]] ? "Yes" : "No");
}
First, note that the numbers will always fit in a long, which allows you to avoid using BigIntever. Second, you need to use Split properly - in this case, the delimiter is a space. Third, there's no reason not to do the whole processing in a single stream - waiting for the whole input, collecting it in memory and then outputting everything at once is a waste of memory. Fourth, note how easy it was to avoid most of the complex checks while incorporating the whole necessary mechanism in simple arithmetic operations.
This runs under 2 seconds on each of the input data, only using ~80kiB of memory.
I think that ideologically, this fits the site perfectly - it's very simple and straightforward and works for all the expected inputs - the perfect hack. Of course, you'd want extra checks if this was for an end-user application, but the HackerEarth site name implies hacks are what's expected, really.

In my experience, frequent Console.WriteLine calls can lead to huge execution times.
Instead of calling that function whenever you want to add some output, I think you should use a StringBuilder object, and append all your output to it. Then, after the for-loop, call Console.WriteLine once to print the StringBuilder's contents.
This might not be your program's biggest problem, but it will help quite a bit.

Myabe by removing casts in these line and using string.compare you cand decrease execution time
if(string.Compare(startf.ToString(), endf.ToString()))
{
Console.WriteLine("Yes");
continue;
}
Console.WriteLine("No");

Fastest way to trim a string and convert it to lower case

I've written a class for processing strings and I have the following problem: the string passed in can come with spaces at the beginning and at the end of the string.
I need to trim the spaces from the strings and convert them to lower case letters. My code so far:
var searchStr = wordToSearchReplacemntsFor.ToLower();
searchStr = searchStr.Trim();
I couldn't find any function to help me in StringBuilder. The problem is that this class is supposed to process a lot of strings as quickly as possible. So I don't want to be creating 2 new strings for each string the class processes.
If this isn't possible, I'll go deeper into the processing algorithm.

Try method chaining.
Ex:
var s = " YoUr StRiNg".Trim().ToLower();

Cyberdrew has the right idea. With string being immutable, you'll be allocating memory during both of those calls regardless. One thing I'd like to suggest, if you're going to call string.Trim().ToLower() in many locations in your code, is to simplify your calls with extension methods. For example:
public static class MyExtensions
{
public static string TrimAndLower(this String str)
{
return str.Trim().ToLower();
}
}

Here's my attempt. But before I would check this in, I would ask two very important questions.
Are sequential "String.Trim" and "String.ToLower" calls really impacting the performance of my app? Would anyone notice if this algorithm was twice as slow or twice as fast? The only way to know is to measure the performance of my code and compare against pre-set performance goals. Otherwise, micro-optimizations will generate micro-performance gains.
Just because I wrote an implementation that appears faster, doesn't mean that it really is. The compiler and run-time may have optimizations around common operations that I don't know about. I should compare the running time of my code to what already exists.
static public string TrimAndLower(string str)
{
if (str == null)
{
return null;
}
int i = 0;
int j = str.Length - 1;
StringBuilder sb;
while (i < str.Length)
{
if (Char.IsWhiteSpace(str[i])) // or say "if (str[i] == ' ')" if you only care about spaces
{
i++;
}
else
{
break;
}
}
while (j > i)
{
if (Char.IsWhiteSpace(str[j])) // or say "if (str[j] == ' ')" if you only care about spaces
{
j--;
}
else
{
break;
}
}
if (i > j)
{
return "";
}
sb = new StringBuilder(j - i + 1);
while (i <= j)
{
// I was originally check for IsUpper before calling ToLower, probably not needed
sb.Append(Char.ToLower(str[i]));
i++;
}
return sb.ToString();
}

If the strings use only ASCII characters, you can look at the C# ToLower Optimization. You could also try a lookup table if you know the character set ahead of time

So first of all, trim first and replace second, so you have to iterate over a smaller string with your ToLower()
other than that, i think your best algorithm would look like this:
Iterate over the string once, and check
whether there's any upper case characters
whether there's whitespace in beginning and end (and count how many chars you're talking about)
if none of the above, return the original string
if upper case but no whitespace: do ToLower and return
if whitespace:
allocate a new string with the right size (original length - number of white chars)
fill it in while doing the ToLower

You can try this:
public static void Main (string[] args) {
var str = "fr, En, gB";
Console.WriteLine(str.Replace(" ","").ToLower());
}