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APC-PRAC-042.c

Problem Statement

Write a function to check whether a given string is a palindrome. Use this function to determine whether an entered string is Palindrome.

Metadata

Property Detail
Author Amit Dutta amitdutta4255@gmail.com
Date 12 Dec 2025
License MIT License (See the LICENSE file for details)
Difficulty Beginner (index: 3 / 10)

Concepts

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  • Pointers
  • Recursion
  • Array
  • Iteration

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Source Code

#include <stdio.h>
#include <string.h>

int isPalindrome(char[]);

int main()
{
    char input[100];
    int len;

    printf("Enter the string (Max: 100 Character): ");
    fgets(input, sizeof(input), stdin);
    len = strlen(input);

    if (len > 0 && input[len - 1] == '\n')
    {
        input[len - 1] = '\0';
    }

    if (isPalindrome(input))
    {
        printf("\nInput string \"%s\" is Palindrome.", input);
    }
    else
    {
        printf("\nInput string \"%s\" is not Palindrome", input);
    }

    return 0;
}

int isPalindrome(char str[])
{
    char *start = str;
    char *end;
    int len = strlen(str);

    if (len == 0)
    {
        return 1;
    }

    end = str + (len - 1);

    while (start < end)
    {
        if (*start != *end)
        {
            return 0;
        }
        start++;
        end--;
    }

    return 1;
}

Explanation

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    You are explaining a C programming code to a beginner.

    STRICT RULES:

    - Only use the given code. Do NOT assume anything not present.

    - Do NOT add extra examples.

    - Keep explanation clear and short.

    - If something is unclear, say "Not clear from code".

    - Follow the exact format below. Do NOT change headings.

    FORMAT:

    [START]

    ## What it does

    (Explain the overall purpose in 1-2 sentences)

    ## Step-by-step

    (Explain how the code works in steps, simple language)

    ## Key Concepts

    (List concepts like loop, condition, function, etc.)

    ## Notes

    (Mention any limitations, errors, or assumptions)

    [END]

    CODE (APC-PRAC-042.c):

    #include <stdio.h>
    #include <string.h>

    int isPalindrome(char[]);

    int main()
    {
        char input[100];
        int len;

        printf("Enter the string (Max: 100 Character): ");
        fgets(input, sizeof(input), stdin);
        len = strlen(input);

        if (len > 0 && input[len - 1] == '\n')
        {
            input[len - 1] = '\0';
        }

        if (isPalindrome(input))
        {
            printf("\nInput string \"%s\" is Palindrome.", input);
        }
        else
        {
            printf("\nInput string \"%s\" is not Palindrome", input);
        }

        return 0;
    }

    int isPalindrome(char str[])
    {
        char *start = str;
        char *end;
        int len = strlen(str);

        if (len == 0)
        {
            return 1;
        }

        end = str + (len - 1);

        while (start < end)
        {
            if (*start != *end)
            {
                return 0;
            }
            start++;
            end--;
        }

        return 1;
    }