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Count words in a given string

Last Updated : 17 Apr, 2024
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Given a string, count the number of words in it. The words are separated by the following characters: space (‘ ‘) or new line (‘\n’) or tab (‘\t’) or a combination of these.

Recommended Practice
Count number of words
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Method 1: The idea is to maintain two states: IN and OUT. The state OUT indicates that a separator is seen. State IN indicates that a word character is seen. We increment word count when previous state is OUT and next character is a word character. 

C++ 
#include <iostream>
#include <cstring>
using namespace std;

#define OUT 0 
#define IN 1 

// Function to count the number of words in a string
int countWords(char* str, int n) {
  if (n == 0) {
    return 0;
  }
  int wordCount = 0;
  int state = OUT; // Initial state is OUT

  // Traverse all characters of the input string
  for (int i = 0; i < n; i++) {
    // Check for backslash first
    if (str[i] == '\\') {
      i++; // Skip next character (after backslash)
      continue;
    }

    // If the current character is a word character
    if (isalnum(str[i])) {
      // If previous state was OUT, increment word count and change state to IN
      if (state == OUT) {
        wordCount++;
        state = IN;
      }
    }
    // If the current character is not a word character
    else {
      // Change state to OUT
      state = OUT;
    }
  }

  return wordCount;
}


// Driver code
int main() { 
    char str[] ="abc\\p\""; // Input string
    cout << "No of words: " << countWords(str, strlen(str)) << endl; // Count words
    return 0; 
}
// This code is contributed by kislay__kumar
C 
#include <stdio.h>
#include <string.h>
#include <ctype.h>

#define OUT 0 
#define IN 1 

// Function to count the number of words in a string
int countWords(char* str, int n) {
  if (n == 0) {
    return 0;
  }
  int wordCount = 0;
  int state = OUT; // Initial state is OUT

  // Traverse all characters of the input string
  for (int i = 0; i < n; i++) {
    // Check for backslash first
    if (str[i] == '\\') {
      i++; // Skip next character (after backslash)
      continue;
    }

    // If the current character is a word character
    if (isalnum(str[i])) {
      // If previous state was OUT, increment word count and change state to IN
      if (state == OUT) {
        wordCount++;
        state = IN;
      }
    }
    // If the current character is not a word character
    else {
      // Change state to OUT
      state = OUT;
    }
  }

  return wordCount;
}

// Driver code
int main() { 
    char str[] ="abc\\p\""; // Input string
    printf("No of words: %d\n", countWords(str, strlen(str))); // Count words
    return 0; 
}
// This code is contributed by kislay__kumar
Java 
public class WordCount {
    // Function to count the number of words in a string
    public static int countWords(String str) {
        if (str.length() == 0) {
            return 0;
        }
        int wordCount = 0;
        int state = 0; // Initial state is OUT

        // Traverse all characters of the input string
        for (int i = 0; i < str.length(); i++) {
            // Check for backslash first
            if (str.charAt(i) == '\\') {
                i++; // Skip next character (after backslash)
                continue;
            }

            // If the current character is a word character
            if (Character.isLetterOrDigit(str.charAt(i))) {
                // If previous state was OUT, increment word count and change state to IN
                if (state == 0) {
                    wordCount++;
                    state = 1;
                }
            }
            // If the current character is not a word character
            else {
                // Change state to OUT
                state = 0;
            }
        }

        return wordCount;
    }

    // Driver code
    public static void main(String[] args) {
        String str = "abc\\p\""; // Input string
        System.out.println("No of words: " + countWords(str)); // Count words
    }
}
// This code is contributed by kislay__kumar
Python3 
import re

# Function to count the number of words in a string
def count_words(string):
    word_count = 0
    state = 0  # Initial state is OUT

    # Traverse all characters of the input string
    for char in re.findall(r"\\.|[\w]", string):
        # Check for backslash first
        if char == '\\':
            continue

        # If the current character is a word character
        if char.isalnum():
            # If previous state was OUT, increment word count and change state to IN
            if state == 0:
                word_count += 1
                state = 1
        # If the current character is not a word character
        else:
            # Change state to OUT
            state = 0

    return word_count

# Driver code
string = "abc\\p\"" # Input string
print("No of words:", count_words(string)) # Count words
"""This code is contributed by kislay__kumar"""
C# 
using System;

class Program
{
    // Function to count the number of words in a string
    static int CountWords(string str)
    {
        if (str.Length == 0)
        {
            return 0;
        }
        int wordCount = 0;
        int state = 0; // Initial state is OUT

        // Traverse all characters of the input string
        foreach (char c in str)
        {
            // Check for backslash first
            if (c == '\\')
            {
                continue;
            }

            // If the current character is a word character
            if (char.IsLetterOrDigit(c))
            {
                // If previous state was OUT, increment word count and change state to IN
                if (state == 0)
                {
                    wordCount++;
                    state = 1;
                }
            }
            // If the current character is not a word character
            else
            {
                // Change state to OUT
                state = 0;
            }
        }

        return wordCount;
    }

    // Driver code
    static void Main()
    {
        string str = "abc\\p\""; // Input string
        Console.WriteLine("No of words: " + CountWords(str)); // Count words
    }
}
// This code is contributed by kislay__kumar
Javascript 
// Function to count the number of words in a string
function countWords(str) {
    if (str.length === 0) {
        return 0;
    }
    let wordCount = 0;
    let state = 0; // Initial state is OUT

    // Traverse all characters of the input string
    for (let i = 0; i < str.length; i++) {
        // Check for backslash first
        if (str[i] === '\\') {
            i++; // Skip next character (after backslash)
            continue;
        }

        // If the current character is a word character
        if (str[i].match(/[a-zA-Z0-9]/)) {
            // If previous state was OUT, increment word count and change state to IN
            if (state === 0) {
                wordCount++;
                state = 1;
            }
        }
        // If the current character is not a word character
        else {
            // Change state to OUT
            state = 0;
        }
    }

    return wordCount;
}

// Driver code
let str = "abc\\p\""; // Input string
console.log("No of words: " + countWords(str)); // Count words
// This code is contributed by kislay__kumar
PHP 
<?php
// Function to count the number of words in a string
function countWords($str) {
    if (strlen($str) === 0) {
        return 0;
    }
    $wordCount = 0;
    $state = 0; // Initial state is OUT

    // Traverse all characters of the input string
    for ($i = 0; $i < strlen($str); $i++) {
        // Check for backslash first
        if ($str[$i] === '\\') {
            $i++; // Skip next character (after backslash)
            continue;
        }

        // If the current character is a word character
        if (ctype_alnum($str[$i])) {
            // If previous state was OUT, increment word count and change state to IN
            if ($state === 
// This code is contributed by kislay__kumar

Output
No of words: 1

Time complexity: O(n)
Auxiliary Space: O(1)

This article is compiled by Aarti_Rathi and Narendra Kangralkar.

Method 2: using String.split() method

  1. Get the string to count the total number of words.
  2. Check if the string is empty or null then return 0.
  3. Use split() method of String class to split the string on whitespaces.
  4. The split() method breaks the given string around matches of the given regular expression and returns an array of string.
  5. The length of the array is the number of words in the given string.
  6. Now, print the result.

Below is the implementation of the above approach:

C++ 
// C++ program to count total
// number of words in the string
#include <bits/stdc++.h>
using namespace std;

// Function to count total number
// of words in the string
int countWords(string str)
{
  // Check if the string is null
  // or empty then return zero
  if (str.size() == 0) {
    return 0;
  }
  // Splitting the string around
  // matches of the given regular
  // expression
  vector<string> words;
  string temp = "";
  for (int i = 0; i < str.size(); i++) {
    if (str[i] == ' ') {
      words.push_back(temp);
      temp = "";
    }
    else {
      temp += str[i];
    }
  }

  int count = 1;

  for (int i = 0; i < words.size(); i++) {
    if (words[i].size() != 0)
      count++;
  }

  // Return number of words
  // in the given string
  return count;
}

int main()
{

  // Given String str
  string str = "abc\\p\"";
  // Print the result
  cout << "No of words : " << countWords(str);
  return 0;
}

// This code is contributed by kislay__kumar
C 
// C program to count total
// number of words in the string
#include <stdio.h>
#include <string.h>

// Function to count total number
// of words in the string
int countWords(char str[])
{
    // Check if the string is null
    // or empty then return zero
    if (strlen(str) == 0) {
        return 0;
    }
    // Splitting the string around
    // matches of the given regular
    // expression
    char* token;
    char* delim = " \n\t";
    token = strtok(str, delim);
    int count = 0;
    while (token != NULL) {
        count++;
        token = strtok(NULL, delim);
    }

    // Return number of words
    // in the given string
    return count;
}

int main()
{
    // Given String str
    char str[] = "abc\\p\"";
    // Print the result
    printf("No of words : %d", countWords(str));
    return 0;
}

// This code is contributed by kislay__kumar
Java 
// Java program to count total
// number of words in the string
import java.io.*;
class GFG 
{
    
    // Function to count total number
    // of words in the string
    public static int 
      countWords(String str)
    {
        
        // Check if the string is null
        // or empty then return zero
        if (str == null || str.isEmpty())
            return 0;
        
        // Splitting the string around
        // matches of the given regular
        // expression
        String[] words = str.split("\\s+");
        
        // Return number of words
        // in the given string
        return words.length;
    }
    
    // Driver Code
    public static void main(String args[])
    {
        
        // Given String str
        String str = "abc\\p\"";
        
        // Print the result
        System.out.println("No of words : " +
           countWords(str));
    }
}
// This code is contributed by kislay__kumar
Python3 
# Python program to count total
# number of words in the string


def countWords(s):

    # Check if the string is null
    # or empty then return zero
    if s.strip() == "":
        return 0

    # Splitting the string

    words = s.split()

    return len(words)


if __name__ == "__main__":
    s = "abc\\p\""
    print("No of words : ", countWords(s))

 """This code is contributed by kislay__kumar"""
C# 
// Include namespace system
using System;


// C# program to count total
// number of words in the string
public class GFG
{
    // Function to count total number
    // of words in the string
    public static int countWords(String str)
    {
        // Check if the string is null
        // or empty then return zero
        if (str == null || str.Length == 0)
        {
            return 0;
        }
        // Splitting the string around
        // matches of the given regular
        // expression
        String[] words = str.Split(" ");
      
      int count = 1;
      
      for(int i=0;i<words.Length;i++){
          if(words[i].Length!=0) count++;
      }
      
        // Return number of words
        // in the given string
        return count;
    }
    // Driver Code
    public static void Main(String[] args)
    {
        // Given String str
        var str = "abc\\p\"";
        // Print the result
        Console.WriteLine("No of words : " + GFG.countWords(str).ToString());
    }
}

// This code is contributed by kislay__kumar
Javascript 
// Javascript program to count total
// number of words in the string

// Function to count total number
// of words in the string
function countWords(str)
{

  // Check if the string is null
  // or empty then return zero
  if (str.length == 0) {
    return 0;
  }
  
  // Splitting the string around
  // matches of the given regular
  // expression
  words = [];
  var temp = "";
  for (var i = 0; i < str.length; i++) {
    if (str[i] == " ") {
      words.push(temp);
      temp = "";
    }
    else {
      temp += str[i];
    }
  }

  var count = 1;

  for (var i = 0; i < words.length; i++) {
    if (words[i].length != 0)
      count++;
  }

  // Return number of words
  // in the given string
  return count;
}

// Driver code
  // Given String str
  var str = "abc\\p\"";
  // Print the result
  console.log("No of words : " +countWords(str));
 
// This code is contributed by kislay__kumar

Output
No of words : 1

Time Complexity: O(N)
Auxiliary Space: O(1)

Method 3:  using StringTokenizer.countTokens() method

  1. Get the string to count the total number of words.
  2. Check if the string is empty or null then return 0.
  3. Create a StringTokenizer with the given string passed as a parameter.
  4. Count the total number of words in the given string using the countTokens() method.
  5. Now, print the result.

Below is the implementation of the above approach:

C++ 
// C++ program to count total
// number of words in the string
#include <bits/stdc++.h>
using namespace std;

// Function to count total number
// of words in the string
int countWords(string s)
{

    // Check if the string is null
    // or empty then return zero
    if (s.empty())
        return 0;

    istringstream is(s);

    int count = 0;

    string line;

    while (getline(is, line, '/'))
        ++count;

    return count;
}
int main()
{
    string str = "abc\\p\"";

    // Print the result
    cout << "No of words: " << countWords(str) << endl;
}
// This code is contributed by kislay__kumar
C 
// C program to count total
// number of words in the string
#include <stdio.h>
#include <string.h>

// Function to count total number
// of words in the string
int countWords(char* s)
{
    // Check if the string is null
    // or empty then return zero
    if (s == NULL || strlen(s) == 0)
        return 0;

    int count = 0;

    char* token = strtok(s, "/");

    while (token != NULL) {
        ++count;
        token = strtok(NULL, "/");
    }

    return count;
}

int main()
{
    char str[] = "abc\\p\"";

    // Print the result
    printf("No of words: %d\n", countWords(str));

    return 0;
}
// This code is contributed by kislay__kumar
Java 
// Java program to count total
// number of words in the string
import java.util.StringTokenizer;

class GFG 
{
    
    // Function to count total number
    // of words in the string
    public static int 
      countWords(String str)
    {
        
        // Check if the string is null
        // or empty then return zero
        if (str    == null || str.isEmpty())
            return 0;
        
        // Create a StringTokenizer with the 
        // given string passed as a parameter
        StringTokenizer tokens = new 
          StringTokenizer(str);
        
        // Return the number of words
        // in the given string using
        // countTokens() method
        return tokens.countTokens();
    }
    
    // Driver Code
    public static void main(String args[])
    {
        
        // Given String str
        String str = "abc\\p\"";
        
        // Print the result
        System.out.println("No of words: " +
          countWords(str));
    }
}
// This code is contributed by kislay__kumar
Python3 
def count_words(s):
    # Check if the string is null or empty then return zero
    if not s:
        return 0

    count = 0
    lines = s.split("/")
    for line in lines:
      
        # Ignore empty lines
        if line.strip():
            count += 1

    return count

s = "abc\\p\""
print("No of words:", count_words(s))

# This code is contributed by kislay__kumar
C# 
// C# program to count total
// number of words in the string
using System;

class GFG
{

  // Function to count total number
  // of words in the string
  public static int
    countWords(String str)
  {

    // Check if the string is null
    // or empty then return zero
    if (string.IsNullOrEmpty(str))
      return 0;

    // Create a String Token with the
    // given string passed as a parameter
    string[] tokens = str.Split(' ');

    // Return the number of words
    // in the given string using
    // Length method
    return tokens.Length;
  }

  // Driver Code
  public static void Main()
  {

    // Given String str
    string str = "abc\\p\"";

    // Print the result
    Console.Write("No of words: " +
                  countWords(str));
  }
}

// This code is contributed by kislay__kumar
Javascript 
// JavaScript program to count total
// number of words in the string

// Function to count total number
// of words in the string
function countWords(s)
{

  // Check if the string is null
  // or empty then return zero
  if (s.length === 0) return 0;
  const lines = s.split("/");
  return lines.length;
}

const str = "abc\\p\"";

// Print the result
console.log(`No of words: ${countWords(str)}`);

// This code is contributed by kislay__kumar

Output
No of words: 1

Time Complexity: O(N)
Auxiliary Space : O(1)

Method 4: using Character.isLetter() method

  1. Get the string to count the total number of words.
  2. Check if the string is empty or null then return 0.
  3. Converting the given string into a character array.
  4. Check if the character is a letter and index of the character array doesn’t equal to the end of the line that means, it is a word and set isWord by true.
  5. Check if the character is not a letter that means there is a space, then we increment the wordCount by one and set the isWord by false.
  6. Check for the last word of the sentence and increment the wordCount by one.
  7. Now, print the result.

Below is the implementation of the above approach:

C++ 
#include <iostream>
#include <ctype.h>  // For isalpha()

using namespace std;

// Function to count total number of words in the string
int countWords(char* str) {
    int wordCount = 0;
    bool isWord = false;

    // Iterate through the string until null terminator (\0)
    for (int i = 0; str[i] != '\0'; i++) {

        // Check if the character is a letter or escaped backslash and set isWord to true
        if (isalpha(str[i]) || (str[i] == '\\' && str[i + 1] != '\0')) { // Handle escaped backslash
            isWord = true;
            // Skip the escaped character if it's a backslash
            if (str[i] == '\\') {
                i++;
            }
        }

        // Increment wordCount if a word ends (space or null terminator)
        else if (!isalpha(str[i]) && !isdigit(str[i]) && isWord) { // Exclude digits for literal interpretation
            wordCount++;
            isWord = false;
        }
    }

    // Handle the last word (if it ends with a letter)
    if (isWord) {
        wordCount++;
    }

    return wordCount;
}

int main() {
    char str[] = "abc\\p\"";
    cout << "No of words : " << countWords(str) << endl;
    return 0;
}
// This code is contributed by kislay__kumar
C 
#include <stdio.h>
#include <ctype.h>  // For isalpha()

// Function to count total number of words in the string
int countWords(char* str) {
    int wordCount = 0;
    int isWord = 0; // false

    // Iterate through the string until null terminator (\0)
    for (int i = 0; str[i] != '\0'; i++) {

        // Check if the character is a letter or escaped backslash and set isWord to true
        if (isalpha(str[i]) || (str[i] == '\\' && str[i + 1] != '\0')) { // Handle escaped backslash
            isWord = 1; // true
            // Skip the escaped character if it's a backslash
            if (str[i] == '\\') {
                i++;
            }
        }

        // Increment wordCount if a word ends (space or null terminator)
        else if (!isalpha(str[i]) && !isdigit(str[i]) && isWord) { // Exclude digits for literal interpretation
            wordCount++;
            isWord = 0; // false
        }
    }

    // Handle the last word (if it ends with a letter)
    if (isWord) {
        wordCount++;
    }

    return wordCount;
}

int main() {
    char str[] = "abc\\p\"";
    printf("No of words : %d\n", countWords(str));
    return 0;
}
// This code is contributed by kislay__kumar
Java 
public class Main {
    // Function to count total number of words in the string
    static int countWords(String str) {
        int wordCount = 0;
        boolean isWord = false;

        // Iterate through the string
        for (int i = 0; i < str.length(); i++) {

            // Check if the character is a letter or escaped backslash and set isWord to true
            if (Character.isLetter(str.charAt(i)) || (str.charAt(i) == '\\' && i + 1 < str.length())) { // Handle escaped backslash
                isWord = true;
                // Skip the escaped character if it's a backslash
                if (str.charAt(i) == '\\') {
                    i++;
                }
            }

            // Increment wordCount if a word ends (space or end of string)
            else if (!Character.isLetter(str.charAt(i)) && !Character.isDigit(str.charAt(i)) && isWord) { // Exclude digits for literal interpretation
                wordCount++;
                isWord = false;
            }
        }

        // Handle the last word (if it ends with a letter)
        if (isWord) {
            wordCount++;
        }

        return wordCount;
    }

    public static void main(String[] args) {
        String str = "abc\\p\"";
        System.out.println("No of words : " + countWords(str));
    }
}
// This code is contributed by kislay__kumar
Python3 
import re

# Function to count total number of words in the string
def count_words(s):
    word_count = 0
    is_word = False

    # Iterate through the string
    for i in range(len(s)):

        # Check if the character is a letter or escaped backslash and set is_word to True
        if s[i].isalpha() or (s[i] == '\\' and i + 1 < len(s)):  # Handle escaped backslash
            is_word = True
            # Skip the escaped character if it's a backslash
            if s[i] == '\\':
                i += 1

        # Increment word_count if a word ends (space or end of string)
        elif not s[i].isalpha() and not s[i].isdigit() and is_word:  # Exclude digits for literal interpretation
            word_count += 1
            is_word = False

    # Handle the last word (if it ends with a letter)
    if is_word:
        word_count += 1

    return word_count

str = "abc\\p\""
print("No of words :", count_words(str))
# This code is contributed by kislay__kumar
C# 
using System;

class Program
{
    // Function to count total number of words in the string
    static int CountWords(string str)
    {
        int wordCount = 0;
        bool isWord = false;

        // Iterate through the string
        for (int i = 0; i < str.Length; i++)
        {
            // Check if the character is a letter or escaped backslash and set isWord to true
            if (char.IsLetter(str[i]) || (str[i] == '\\' && i + 1 < str.Length)) // Handle escaped backslash
            {
                isWord = true;
                // Skip the escaped character if it's a backslash
                if (str[i] == '\\')
                {
                    i++;
                }
            }

            // Increment wordCount if a word ends (space or end of string)
            else if (!char.IsLetter(str[i]) && !char.IsDigit(str[i]) && isWord) // Exclude digits for literal interpretation
            {
                wordCount++;
                isWord = false;
            }
        }

        // Handle the last word (if it ends with a letter)
        if (isWord)
        {
            wordCount++;
        }

        return wordCount;
    }

    static void Main(string[] args)
    {
        string str = "abc\\p\"";
        Console.WriteLine("No of words : " + CountWords(str));
    }
}
// This code is contributed by kislay__kumar
Javascript 
// Function to count total number of words in the string
function countWords(str) {
    let wordCount = 0;
    let isWord = false;

    // Iterate through the string
    for (let i = 0; i < str.length; i++) {

        // Check if the character is a letter or escaped backslash and set isWord to true
        if (/[a-zA-Z]/.test(str[i]) || (str[i] === '\\' && i + 1 < str.length)) { // Handle escaped backslash
            isWord = true;
            // Skip the escaped character if it's a backslash
            if (str[i] === '\\') {
                i++;
            }
        }

        // Increment wordCount if a word ends (space or end of string)
        else if (!/[a-zA-Z0-9]/.test(str[i]) && isWord) { // Exclude digits for literal interpretation
            wordCount++;
            isWord = false;
        }
    }

    // Handle the last word (if it ends with a letter)
    if (isWord) {
        wordCount++;
    }

    return wordCount;
}

let str = "abc\\p\"";
console.log("No of words :", countWords(str));
// This code is contributed by kislay__kumar

Output
No of words : 1

Time Complexity: O(N)
Auxiliary Space: O(1) 



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