🔖 Check Palindrome in C with and without Function

⬅️ Back

🧪 Check if a String is a Palindrome in C

This tutorial shows you how to check if a string is a palindrome in C. A palindrome is a word or sentence that reads the same forwards and backwards. For example, "madam" or "A man a plan a canal Panama".

We’ll ignore case and spaces while checking. Two versions are shown:

• ✅ Using a separate function
• 🛠️ Without using any function

---

✅ Method 1: With Function (Ignoring Case & Spaces)

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

void removeSpacesAndToLower(char *src, char *cleaned) {
    int j = 0;
    for (int i = 0; src[i] != '\0'; i++) {
        if (!isspace(src[i])) {
            cleaned[j++] = tolower(src[i]);
        }
    }
    cleaned[j] = '\0';
}

int isPalindrome(char *str) {
    int start = 0;
    int end = strlen(str) - 1;

    while (start < end) {
        if (str[start] != str[end]) {
            return 0; // Not palindrome
        }
        start++;
        end--;
    }
    return 1; // Palindrome
}

int main() {
    char input[100], cleaned[100];

    printf("Enter a string: ");
    fgets(input, sizeof(input), stdin);

    removeSpacesAndToLower(input, cleaned);

    if (isPalindrome(cleaned)) {
        printf("✅ The string is a palindrome.\n");
    } else {
        printf("❌ The string is NOT a palindrome.\n");
    }

    return 0;
}

🧠 Explanation:

• removeSpacesAndToLower() cleans the input by removing spaces and converting all letters to lowercase.
• isPalindrome() compares the cleaned string from both ends.

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🛠️ Method 2: Without Function (All logic inside main())

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

int main() {
    char input[100], cleaned[100];
    int i, j = 0;

    printf("Enter a string: ");
    fgets(input, sizeof(input), stdin);

    // Remove spaces and convert to lowercase
    for (i = 0; input[i] != '\0'; i++) {
        if (!isspace(input[i])) {
            cleaned[j++] = tolower(input[i]);
        }
    }
    cleaned[j] = '\0';

    // Check palindrome
    int start = 0, end = strlen(cleaned) - 1;
    int is_palindrome = 1;

    while (start < end) {
        if (cleaned[start] != cleaned[end]) {
            is_palindrome = 0;
            break;
        }
        start++;
        end--;
    }

    if (is_palindrome) {
        printf("✅ The string is a palindrome.\n");
    } else {
        printf("❌ The string is NOT a palindrome.\n");
    }

    return 0;
}

🔍 Output Examples:

Enter a string: Madam
✅ The string is a palindrome.

Enter a string: Hello
❌ The string is NOT a palindrome.

Enter a string: A man a plan a canal Panama
✅ The string is a palindrome.

---

📌 Summary

Checking for palindromes in C teaches you about string manipulation, ignoring whitespace, case conversion, and index-based comparison. Practicing both with and without functions builds solid C fundamentals.

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