How can I retrieve the count of a certain character in a string array?

Question

I have this code to try to get a count of how many of the passed-in characters occurs in a string array:

string[] doc1StrArray;
. . .
private int GetCountOfSpecificCharacter(string CharToCount)
{
    int count = 0;
    count = doc1StrArray.Count(f => f == CharToCount);
    return count;
}

...called like so:

iCountOfCommasInDoc1 = GetCountOfSpecificCharacter(",");

...but it doesn't work. It finds no commas, for example, in the following case, although the document certainly does contain commas.

UPDATE

Both are working - Roman's suggestion and Teroneko's:

private int GetCountOfSpecificCharacterInDoc1(char CharToCount)
{
    return doc1StrArray.Sum(s => s.Count(c => c == CharToCount));
}

private int GetCountOfSpecificCharacterInDoc2(char CharToCount)
{
    return doc2StrArray.SelectMany(x => x).Count(c => c == CharToCount);
}

...but I don't know which one is better/more efficient.

You are comparing the string against the character if I am not mistaken. You'll need to check against every character in each string in your array — Jawad
– Jawad, Commented Jun 21, 2020 at 23:00
Maybe also: return string.Join("", doc1StrArray).Aggregate(0, (i, c) => c.Equals(CharToCount) ? ++i : i); — user10216583
– user10216583, Commented Jun 22, 2020 at 15:36

teslae · Accepted Answer · 2020-06-22 06:48:34Z

5

private int GetCountOfSpecificCharacter(char charToCount)
{
    int count = 0;
    foreach (var word in doc1StrArray)
        foreach (char character in word)
           if (character == charToCount)
               count++;
    return count;
}

edited Jun 22, 2020 at 6:48

answered Jun 21, 2020 at 23:43

teslae

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1 Comment

Arman Ebrahimpour Over a year ago

Most efficient way among all answers

Jawad · Accepted Answer · 2020-06-22 00:38:29Z

This is a sample of what you can use to iterate over an array of strings to check the number of times a character appears in the string and then sum it all up.

string[] test = new string[] { 
    "This is, the first test string", 
    "This, is the second, test string", 
    "this is the, third"};

string inp = ",";
Console.WriteLine(test.Sum(stringItem => stringItem.Count(charItem => charItem.ToString().Equals(inp))));

// Prints 4

During the comparison, you can convert the character being iterated to a string for a proper string.Equals(string) comparison. Reason you want to convert it to a string is because character 'a' is Not equal to a string "a". If you want to do a character comparison, see the character compare method below (but note characters should be compared with characters and strings with strings.).

This can be your method to count,

private int GetCountOfSpecificCharacter(string CharToCount)
{
    return doc1StrArray.Sum(stringItem => stringItem.Count(charItem => charItem.ToString().Equals(CharToCount)));
}

// And this one to use for Character Comparisons using `.ToCharArray()` method. 
// You can parse each character as well by the use of char.Parse(str)
private int GetCountOfSpecificCharacter(string CharToCount)
{
    return test.Sum(stringItem => stringItem.ToCharArray().Count(charItem => charItem.Equals(CharToCount.ToCharArray().First())));
}

Teneko · Accepted Answer · 2020-06-24 11:02:14Z

@Jawad is right. You can do something like this to accomplimish your goal:

var count = doc1StrArray.SelectMany(x => x).Count(c => c == CharToCount);

This selects any character in each array item and returns them as one IEnumerable<char>. When you know apply .Count(..) on it, you are counting against each character.

Edit: I made some tests and it seems that the for-loop is the fastest

        public int GetAmountOfChar(string[] strings, char character) {
            int amountOfChar = 0;
            var linesLength = strings.Length;
            for (var lineIndex = 0; lineIndex < linesLength; lineIndex++)
            {
                var line = TextExample[lineIndex];
                var charsLength = line.Length;
                for (var charIndex = 0; charIndex < charsLength; charIndex++)
                    if (line[charIndex] == character)
                        amountOfChar++;
            }
            return amountOfChar;
        }

but not the foreach-loop:

[TestSelectManyCount] Found 5861172 characters in 3295,8278ms
[TestForForIncrement] Found 5861172 characters in 377,0376ms
[TestForCount] Found 5861172 characters in 1064,9164ms
[TestForEachWhileIndexOfIncrement] Found 5861172 characters in 1550,894ms
[TestForEachForEachIncrement] Found 5861172 characters in 473,4347ms
[TestSumCounts] Found 5861172 characters in 1062,2644ms

using System;
using System.Diagnostics;
using System.Linq;

namespace StackOverflow._62505315
{
    public partial class Program
    {
        public const char CharToBeFound = 'a';
        public const int Iterations = 5000;

        static Stopwatch stopWatch = new Stopwatch();

        static void Main(string[] args)
        {
            TestSelectManyCount();
            TestForForIncrement();
            TestForCount();
            TestForEachWhileIndexOfIncrement();
            TestForEachForEachIncrement();
            TestSumCounts();
        }

        public static void TestSelectManyCount()
        {
            var iterations = Iterations;
            int amountOfChar = 0;
            stopWatch.Start();
            checked
            {
                while (iterations-- >= 0)
                {
                    amountOfChar += TextExample.SelectMany(x => x).Count(c => c == CharToBeFound);
                }
            }
            stopWatch.Stop();
            Console.WriteLine($"[{nameof(TestSelectManyCount)}] Found {amountOfChar} characters in {stopWatch.Elapsed.TotalMilliseconds}ms");
            stopWatch.Reset();
        }

        public static void TestForForIncrement()
        {
            var iterations = Iterations;
            int amountOfChar = 0;
            stopWatch.Start();
            checked
            {
                while (iterations-- >= 0)
                {
                    var linesLength = TextExample.Length;
                    for (var lineIndex = 0; lineIndex < linesLength; lineIndex++)
                    {
                        var line = TextExample[lineIndex];
                        var charsLength = line.Length;
                        for (var charIndex = 0; charIndex < charsLength; charIndex++)
                            if (line[charIndex] == CharToBeFound)
                                amountOfChar++;
                    }
                }
            }
            stopWatch.Stop();
            Console.WriteLine($"[{nameof(TestForForIncrement)}] Found {amountOfChar} characters in {stopWatch.Elapsed.TotalMilliseconds}ms");
            stopWatch.Reset();
        }

        public static void TestForCount()
        {
            var iterations = Iterations;
            var amountOfChar = 0;
            stopWatch.Start();
            checked
            {
                while (iterations-- >= 0)
                {
                    var lineLength = TextExample.Length;
                    for (var lineIndex = 0; lineIndex < lineLength; lineIndex++)
                    {
                        amountOfChar += TextExample[lineIndex].Count(c => c == CharToBeFound);
                    }
                }
            }
            stopWatch.Stop();
            Console.WriteLine($"[{nameof(TestForCount)}] Found {amountOfChar} characters in {stopWatch.Elapsed.TotalMilliseconds}ms");
            stopWatch.Reset();
        }

        public static void TestForEachWhileIndexOfIncrement()
        {
            var iterations = Iterations;
            var amountOfChar = 0;
            stopWatch.Start();
            checked
            {
                while (iterations-- >= 0)
                {
                    foreach (string word in TextExample)
                    {
                        int startIndex = 0;
                        int charIndex = 0;
                        while ((charIndex = word.IndexOf(CharToBeFound, startIndex)) != -1)
                        {
                            startIndex = charIndex + 1;
                            amountOfChar++;
                        }
                    }
                }
            }
            stopWatch.Stop();
            Console.WriteLine($"[{nameof(TestForEachWhileIndexOfIncrement)}] Found {amountOfChar} characters in {stopWatch.Elapsed.TotalMilliseconds}ms");
            stopWatch.Reset();
        }

        public static void TestForEachForEachIncrement()
        {
            var iterations = Iterations;
            int amountOfChar = 0;
            stopWatch.Start();
            checked
            {
                while (iterations-- >= 0)
                {
                    foreach (var word in TextExample)
                        foreach (char character in word)
                            if (character == CharToBeFound)
                                amountOfChar++;
                }
            }
            stopWatch.Stop();
            Console.WriteLine($"[{nameof(TestForEachForEachIncrement)}] Found {amountOfChar} characters in {stopWatch.Elapsed.TotalMilliseconds}ms");
            stopWatch.Reset();
        }

        public static void TestSumCounts()
        {
            var iterations = Iterations;
            int amountOfChar = 0;
            stopWatch.Start();
            checked
            {
                while (iterations-- >= 0)
                {
                    amountOfChar += TextExample.Sum(s => s.Count(c => c == CharToBeFound));
                }
            }
            stopWatch.Stop();
            Console.WriteLine($"[{nameof(TestSumCounts)}] Found {amountOfChar} characters in {stopWatch.Elapsed.TotalMilliseconds}ms");
            stopWatch.Reset();
        }
    }
}

For my surprise I also found a reference here that does underline the fact, that the for-loop is outscaling the foreach-loop

With this also I get "Operator '==' cannot be applied to operands of type 'char' and 'string'"
I had to assume that CharToCount is a character: char CharToCount = 'b', and doc1StrArrayis an array of character enumerables (something like char[]): string[] arrays = new string[] { "testa", "testb" }. Please provide us the full code, then we can help concretely.

Roman Kalinchuk · Accepted Answer · 2020-06-21 23:04:16Z

2

Or like this

private int GetCountOfSpecificCharacter(string[] doc1StrArray, char charToCount)
{
    int count = 0;
    count = doc1StrArray.Sum(s => s.Count(c => c == charToCount));
    return count;
}

answered Jun 21, 2020 at 23:04

Roman Kalinchuk

7283 silver badges14 bronze badges

2 Comments

B. Clay Shannon-B. Crow Raven Over a year ago

I get "Operator '==' cannot be applied to operands of type 'char' and 'string'"

Roman Kalinchuk Over a year ago

@B.ClayShannon have you changed CharToCount type to char?

user7512953 · Accepted Answer · 2020-06-24 15:53:16Z

1

You could implement with parallel linq.

    public static int GetBounty(string[] gettysburgLines, char c)
    {
        int count = 0;
        gettysburgLines.AsParallel().ForAll(line => {
            int q = line.AsParallel().Where(a => a == c).Count();
            count += q;
        });
        return count;
    }

answered Jun 24, 2020 at 15:53

user7512953

Comments

BeNes · Accepted Answer · 2020-06-25 01:33:28Z

1

You can also make use of Regex:

private int GetCountOfSpecificCharacter(string CharToCount)
{
    return Regex.Matches(string.join("", doc1StrArray), CharToCount).Count;
}

answered Jun 25, 2020 at 1:33

BeNes

887 bronze badges

Comments

Lee Taylor · Accepted Answer · 2022-06-16 23:35:07Z

1

just use :

var ad = Array.FindAll(yourArray,u=>u.Equals(passedChar).Length

edited Jun 16, 2022 at 23:35

Lee Taylor

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answered Jun 16, 2022 at 7:43

AmirAsadi

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