The objective of this exercise is to propose a new algorithm to check if a word (string without spaces) is palindrome.

• Write the function "firstlast" that takes as parameter a word (a string without spaces) and construct a new string by regrouping the characters as follows : the first and the last, the second and before the last, and so one. Example : abcdefg --> agbfced
• Notice that if the previous function is applied on a palindrome word (example: laval --> llaav), the generated string is composed of a pair of identical characters (except the last character if the original string length is odd). Write the function "isPalindrome" that verifies if a word string is palindrome, using the function "firstlast".
• Write a main program that prompts the user to enter a string and verifies if it is or not, using the previous functions.

#include <stdio.h>
#define size 100

void firstlast(char in[], char out[])
{
    int i, j;
    for(j=0;in[j];j++);
    j--;
    
    for(i=0;i<=j/2;i++)
    {
        out[2*i] = in[i];
        out[2*i+1] = in[j-i];
    }
    out[j+1]='\0' ;   
}

int isPalindrome(char in[])
{
    char out[size];
    int i;
    
    firstlast(in,out);
    printf("%s\n",out);
    for(i=0;out[i];i+=2)
        if(out[i+1] && out[i]!=out[i+1])
            return 0;
    return 1;
}


int main()
{
    char in[size];

    printf("Enter a word: ");
    scanf("%s",in);
    if(isPalindrome(in))
        printf("\"%s\" is palindrome\n", in);
    else
        printf("\"%s\" is not palindrome\n", in);

    return 0;
}