1258 - Making Huge Palindromes

#include <bits/stdc++.h>
using namespace std;
int prefix[1000005];
void setPrefix(string s)
{

    prefix[0] = -1;
    int j =-1, i = 0;
    reverse(s.begin(), s.end());
    int len = s.length();
    while(i < len)
    {
        while(j >= 0 and s[i] != s[j])
        {
            j = prefix[j];
        }
        i++;
        j++;
        prefix[i] = j;
    }
}
int kmp_algorithm(string s)
{
    int i = 0 , j = 0;
    string p ,t = s;
    reverse(s.begin(), s.end());
    int n = t.length();
    int m = s.length();
    p = s;

    while(i < n)
    {
        while(j >= 0 and t[i] != p[j])
        {
            j = prefix[j];
        }
        j++;
        i++;
    }
    return j;
}
int main()
{
    int tes , o = 0;
    cin >> tes;
    while(tes--)
    {
        o++;
        string s, s1;
        cin >> s;
        setPrefix(s);
        int res = (2 * s.length()) - kmp_algorithm(s);
        printf("Case %d: %d\n", o , res);
    }
}