Palindrome in C without Using String Functions: A Comprehensive Guide

Introduction

This blog post is aimed at shedding light on the palindrome theory and taking a deeper look into how it is possible to code palindromes in C. The special thing about this program is that there will be no use of standard string functions such as strlen() or array indexing for reversing the string. We will cover what is meant by a palindrome, explain how the algorithm works, share some C code examples which do not make use of string functions and provide outputs.

Understanding Palindromes

A palindrome is any arrangement of characters that reads the same backwards as forwards. This holds true for words, phrases, numbers and other sequences of characters. Some of these words include level, radar and civic among others. Similarly palindromic phrases or numbers are read backwards with symmetry.

Algorithm for Palindrome Checking without String Functions

The algorithm used to determine whether a given string is a palindrome without using string functions entails iterating over the string from both ends and comparing characters. Below are the steps:

Input: Get the word to test if it’s a palindrome or not.

Initialization: Create two pointers, the first one is located at the beginning of string while the second one is at the end.

Comparison: Check whether the characters in pointer 1 and pointer 2 match. In case they do, move both pointers inwards. Otherwise, it means that it’s not a palindrome.

Repeat: Iterate through each letter as given by pointer 1 and compare this with its corresponding opposite character as defined by pointer 2.

Check for Palindrome: If the pointers meet then it implies that input is palindrome but if not then no its not.

Palindromic Program in C without String Functions

Now, let’s write a C program to implement palindrome checking algorithm without making use of standard functions.

#include <stdio.h>

int isPalindrome(char str[]) {
    int start = 0;
    int end = 0;

    // Move 'end' to the last character of the string
    while (str[end] != '\0') {
        end++;
    }
    end--;

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

    return 1; // Palindrome
}

int main() {
    char inputString[100];

    printf("Enter a string: ");
    scanf("%s", inputString);

    if (isPalindrome(inputString)) {
        printf("%s is a palindrome.\n", inputString);
    } else {
        printf("%s is not a palindrome.\n", inputString);
    }

    return 0;
}

Output Example

Example: Palindrome String without String Functions

Enter a string: radar
radar is a palindrome.

Explanation

The program gives the definition of a function isPalindrome that checks if a specified string is a palindrome. The starting and ending pointers are used to traverse through the string from both ends without using any string operation. These pointers are moved inwards as comparison takes place among letters until they meet at the middle.

Conclusion

Developing C code to determine whether phrases have the same spelling but without using string operations helps one to understand strings differently. So, though it remains simple, the way standard string functions are not there enables deeper knowledge of how C handles pointers.

In conclusion, feel free to play with the given C code in your C development environment. Please don’t hesitate to ask anything you do not know or may encounter difficulties with or for further information on palindromes and c programming.