C PROGRAMMING PROGRAM • STRINGS

Count Words in a Sentence

Learn how to count words in a sentence using a clear C program.

BeginnerStringsisspace()State flag

PROBLEM UNDERSTANDING

Input and expected output

Sample input

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Sample output

Word count = 5

COMPLETE C PROGRAM

Complete C implementation

#include <stdio.h>
#include <ctype.h>

int main(void)
{
    char text[500];
    int words = 0, insideWord = 0;

    fgets(text, sizeof text, stdin);
    for (int index = 0; text[index] != '\0'; index++) {
        if (isspace((unsigned char) text[index])) {
            insideWord = 0;
        } else if (!insideWord) {
            words++;
            insideWord = 1;
        }
    }
    printf("Word count = %d\n", words);
    return 0;
}

CURRENT STEP

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SELECTED LINE

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EXPECTED OUTPUT FOR THE SAMPLE

Word count = 5

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Count each transition from whitespace into a non-whitespace sequence.
Display the computed result.

Count each transition from whitespace into a non-whitespace sequence.

EFFICIENCY

Time and space complexity

Time complexity

O(n)

Auxiliary space

O(1)

DEBUGGING CHECKLIST

Common mistakes

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Use the correct format specifier for every variable.

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Initialize variables before using their values.

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Check braces, semicolons and input order carefully.

Try it yourself

Practice: Run the program with the sample input, predict its output, and then test one boundary case of your own.