C# Program to Count Words in a String

You can count words in a string in C# by splitting the string with string.Split(' ', StringSplitOptions.RemoveEmptyEntries) and then getting the length of the resulting array with .Length.

Examples

InputHello world

Output2

Input This is a simple test string.

Output6

Input

Output0

How to Think About It

To count words, think of words as groups of characters separated by spaces. We split the string by spaces, ignore empty parts caused by extra spaces, and count how many parts remain.

Algorithm

1

Get the input string.

2

Split the string by spaces, ignoring empty entries.

3

Count the number of parts in the split result.

4

Return or print the count.

Code

csharp

using System;

class Program {
    static void Main() {
        string input = "Hello world from C#";
        string[] words = input.Split(' ', StringSplitOptions.RemoveEmptyEntries);
        int count = words.Length;
        Console.WriteLine(count);
    }
}

Output

4

Dry Run

Let's trace the input "Hello world from C#" through the code.

1

Input string

input = "Hello world from C#"

2

Split string by spaces

words = ["Hello", "world", "from", "C#"]

3

Count words

count = 4

4

Print result

Output: 4

Step	Words Array
Split	["Hello", "world", "from", "C#"]

Why This Works

Step 1: Splitting the string

Using Split(' ', StringSplitOptions.RemoveEmptyEntries) breaks the string into parts separated by spaces and ignores empty parts caused by multiple spaces.

Step 2: Counting words

The length of the resulting array gives the number of words because each element is one word.

Alternative Approaches

Using Regex to split by any whitespace

csharp

using System;
using System.Text.RegularExpressions;

class Program {
    static void Main() {
        string input = "Hello   world\nfrom C#";
        string[] words = Regex.Split(input.Trim(), "\\s+");
        Console.WriteLine(words.Length);
    }
}

This handles all whitespace like tabs and new lines, but requires importing Regex and may be slower.

Counting words by iterating characters

csharp

using System;

class Program {
    static void Main() {
        string input = "Hello world from C#";
        int count = 0;
        bool inWord = false;
        foreach (char c in input) {
            if (char.IsWhiteSpace(c)) {
                if (inWord) count++;
                inWord = false;
            } else {
                inWord = true;
            }
        }
        if (inWord) count++;
        Console.WriteLine(count);
    }
}

This method counts words manually without splitting, useful for custom definitions but more complex.

Complexity: O(n) time, O(n) space

Time Complexity

Splitting the string scans each character once, so it takes linear time proportional to the string length.

Space Complexity

The split method creates an array of words, so space grows with the number of words.

Which Approach is Fastest?

Simple split with StringSplitOptions.RemoveEmptyEntries is fastest and easiest for normal cases; regex is slower but more flexible; manual counting uses less memory but is more complex.

Approach	Time	Space	Best For
Split with RemoveEmptyEntries	O(n)	O(n)	Simple and common cases
Regex Split	O(n)	O(n)	Handling all whitespace types
Manual Counting	O(n)	O(1)	Custom word definitions, low memory