Longest palindrome

input/code.cpp: In function 'int main()':
input/code.cpp:66:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   66 |     scanf("%s", s);
      |     ~~~~~^~~~~~~~~

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N=1000005;

char Ma[2*N];
int Mp[2*N];
void Manacher(char s[], int len)
{
    int l = 0;
    Ma[l++] = '$';
    Ma[l++] = '#';
    for(int i=0; i<len; i++)
    {
        Ma[l++] = s[i];
        Ma[l++] = '#';
    }
    Ma[l] = 0;
    int mx = 0, id = 0;
    for(int i=0; i<l; i++)
    {
        if(mx > i)
            Mp[i] = min(Mp[2*id - i], mx-i);
        else
            Mp[i] = 1;

        while(Ma[i + Mp[i]] == Ma[i - Mp[i]])
            Mp[i]++;

        if(Mp[i]+i > mx)
        {
            mx = i+Mp[i];
            id = i;
        }
    }
    mx = 0, id = 0;
    for(int i=0; i<l; i++)
        if(Mp[i] > mx)
        {
            mx = Mp[i];
            id = i;
        }
    vector<char> ans;
    for(int i = 1; i<mx; i++)
    {
        char c = Ma[id - i];
        if(c != '#' && c != '$')
            ans.push_back(c);
    }

    reverse(ans.begin(), ans.end());
    for(char c: ans)
        putchar(c);
    if(Ma[id] != '#')
        putchar(Ma[id]);
    reverse(ans.begin(), ans.end());
    for(char c: ans)
        putchar(c);
    
}

char s[N];
int main()
{
    // Test();
    scanf("%s", s);
    int len = strlen(s);
    Manacher(s, len);
    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED