C Program to Find Input String Is Polindrome Or Not Using While Loop

C Program To Find Input String Is Polindrome Or Not Using While Loop

This c program uses the while loop and character array and finds the whether input string is a polindrome or not.

Algorithm:

1) Finds the length of the input string.
2) Getting reverse string using string length.
3) Compares reverse string with input string, input sting is a polindrome if both same, otherwise not.

String Polindrome Or Not C Program:

#include<stdio.h>                                                               
                                                                                                                                                             
int main()                                                                      
{                                                                               
    char str[20], reverse_str[25];                                              
    int  i, len = 0;                                                            
                                                                                
    printf("Enter a string: ");                                                 
    gets(str);                                                                  
            
    //Gets the string length                                                                    
    while (str[len] != '\0')                                                    
    {                                                                           
        len++;                                                                  
    }                                                                           
           
    //reverse string                                                                     
    i = 0;                                                                      
    while (i < len)                                                             
    {                                                                           
       reverse_str[i] = str[len-i-1];                                           
       i++;                                                                     
    }                                                                           
    reverse_str[i] = '\0';                                                      
    //Compares and checks whether input string is polindrome or not.
    i = 0;                                                                      
    while (i < len)                                                             
    {                                                                           
        if (reverse_str[i] != str[i])                                           
        {                                                                       
           printf("%s is not a palindrome.\n", str);                            
           return 0;                                                            
        }                                                                       
                                                                                
        i++;                                                                    
    }                                                                           
    printf("%s is a palindrome.\n", str);                                       
    return 1;                                                                   
}                                                                
                                                                                  

$ cc string-polindrome.c 
string-polindrome.c: In function ‘main’:
string-polindrome.c:9:5: warning: implicit declaration of function ‘gets’ [-Wimplicit-function-declaration]
     gets(str);
     ^~~~
/tmp/ccs2K9ca.o: In function `main':
string-polindrome.c:(.text+0x2b): warning: the `gets' function is dangerous and should not be used.
$ ./a.out 
Enter a string: malayalam
malayalam is a palindrome.

$ ./a.out 
Enter a string: testing
testing is not a palindrome.