Count words in a given string

1.8

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

There can be many solutions to this problem. Following is a simple and interesting solution.
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/C++

/* C/C++ program to count no of words from given input string. */
#include <stdio.h>

#define OUT    0
#define IN    1

// returns number of words in str
unsigned countWords(char *str)
{
    int state = OUT;
    unsigned wc = 0;  // word count

    // Scan all characters one by one
    while (*str)
    {
        // If next character is a separator, set the 
        // state as OUT
        if (*str == ' ' || *str == '\n' || *str == '\t')
            state = OUT;

        // If next character is not a word separator and 
        // state is OUT, then set the state as IN and 
        // increment word count
        else if (state == OUT)
        {
            state = IN;
            ++wc;
        }

        // Move to next character
        ++str;
    }

    return wc;
}

// Driver program to tes above functions
int main(void)
{
    char str[] = "One two         three\n    four\tfive  ";
    printf("No of words : %u", countWords(str));
    return 0;
}

Java

/* Java program to count no of words
from given input string. */
public class GFG {
 
    static final int OUT = 0;
    static final int IN = 1;
     
    // returns number of words in str
    static int countWords(String str)
    {
        int state = OUT;
        int wc = 0;  // word count
        int i = 0;
        
        // Scan all characters one by one
        while (i < str.length())
        {
            // If next character is a separator, set the 
            // state as OUT
            if (str.charAt(i) == ' ' || str.charAt(i) == '\n' 
                    || str.charAt(i) == '\t')
                state = OUT;
                
     
            // If next character is not a word separator
            // and state is OUT, then set the state as IN
            // and increment word count
            else if (state == OUT)
            {
                state = IN;
                ++wc;
            }
     
            // Move to next character
            ++i;
        }
        return wc;
    }
     
    // Driver program to test above functions
    public static void main(String args[])
    {
        String str = "One two       three\n four\tfive  ";
        System.out.println("No of words : " + countWords(str));
    }
}
// This code is contributed by Sumit Ghosh

Python

# Python program to count words in a given string
OUT = 0
IN = 1

# Returns number of words in string
def countWords(string):
    state = OUT
    wc = 0

    # Scan all characters one by one
    for i in xrange(len(string)):

        # If next character is a separator, set the
        # state as OUT
        if (string[i] == ' ' or string[i] == '\n' or
            string[i] == '\t'):
            state = OUT

        # If next character is not a word separator
        # and state is OUT, then set the state as
        # IN and increment word count
        elif state == OUT:
            state = IN
            wc+=1

    # Return the number of words
    return wc

# Driver program
string = "One two         three\n  four\tfive  "
print "No. of words : " + str(countWords(string))

# This code is contributed by BHAVYA JAIN


Output:
No of words : 5

Time complexity: O(n)

This article is compiled by Narendra Kangralkar. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

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