Palindrome Index : HackerRank Problem Solution

You are given a  string of lowercase letters. Your task is to figure out the index of the character on whose removal it will make the string a palindrome. There will always be a valid solution.

In case the string is already a palindrome, then -1 is also a valid answer along with possible indices.


Input:

3
aaab
baa
aaa

Output:

3
0
-1

Implementation:

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#define MAX 1000000

int ispalindrome(char *s)
    {
    int l=0;
    int r=strlen(s)-1;
    while(l<r)
        {
        if(*(s+l)!=*(s+r))
            return 0;
        l++;
        r--;
    }
    return 1;
}

int removechar(char *s,int index)
    {
    char *v;
    int i=0,j=0;
    v=(char*)malloc(sizeof(char)*MAX);
    while(*(s+i))
        {
        if(i==index)
            {
            /*if(j>0)
                j--;
            continue;*/
            i++;
        }
        else
            {
            v[j]=s[i];
            i++;
            j++;
        }
    }
    v[j]='\0';
    if(ispalindrome(v))
        return 1;
    else
        return 0;
}

int main() {

    int t,l,r;
    char *s;
    s=(char*)malloc(sizeof(char)*MAX);
    scanf("%d",&t);
    while(t--)
        {
        scanf("%s",s);
        l=0;
        r=strlen(s)-1;
        if(ispalindrome(s))
            {
            printf("-1\n");
            continue;
        }
        while(l<r)
            {
            if(*(s+l)==*(s+r))
                {
                l++,r--;
            }
            else
                {
                //first mismatch
                if(removechar(s,l))
                    {
                    printf("%d\n",l);
                    break;
                }
                else if(removechar(s,r))
                    {
                    printf("%d\n",r);
                    break;
                }
            }
        }
    }
    return 0;
}