String padding

input/code.cpp: In function 'void solve()':
input/code.cpp:32:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   32 |     for (int i = 0; i < s.size(); i++)
      |                     ~~^~~~~~~~~~
input/code.cpp:39:22: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |             while (r < s.size() && s[l] == s[r])
      |                    ~~^~~~~~~~~~
input/code.cpp:58:26: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   58 |                 while (r < s.size() && s[l] == s[r])
      |                        ~~^~~~~~~~~~
input/code.cpp:68:25: warning: comparison of integer expressions of d...

#include <iostream>
#include <vector>
#include <array>
#include <string>
#include <algorithm>
#include <numeric>
#include <unordered_map>
#include <unordered_set>
#include <set>
#include <queue>
#include <climits>
#include <cmath>
#include <functional>
#include <type_traits>
#include <bitset>
#include <fstream>
 
#define int long long
using namespace std;

int mod = 1000000007;

void solve() {
    int n;
    string s;
    cin >> n >> s;

    vector<int> zArr(s.size());
    vector<int> res;
 
    int l = 0, r = 0;
    for (int i = 0; i < s.size(); i++)
    {
        if (i > r)
        {
            // Use naive
            r = i;
            l = 0;
            while (r < s.size() && s[l] == s[r])
            {
                l++;
                r++;
            }
            r--;
            l = i;
            zArr[i] = r-i+1;
        }
        else
        {
            if (zArr[i-l] < r-i+1)
            {
                zArr[i] = zArr[i-l];
            }
            else
            {
                l = r-i+1;
                r = r+1;
                while (r < s.size() && s[l] == s[r])
                {
                    l++;
                    r++;
                }
                l = i;
                r--;
                zArr[i] = r-l+1;
            }
        }
        if (zArr[i] + i == s.size())
            res.push_back(zArr[i]);
    }
    /*
    for (int i = res.size()-1; i >= 0; i--)
    {
        cout << res[i] << " ";
    }
    */

    vector<int> mult(n);
    mult[0] = 1;
    for (int i = 1; i < mult.size(); i++)
        mult[i] = (mult[i-1] * 26) % mod;

    vector<int> dp(n);
    for (int i = 0; i < s.size(); i++)
    {
        dp[i] = 0;
    }
    dp[s.size()-1] = 1;


    for (int i = s.size(); i < dp.size(); i++)
    {
        dp[i] = mult[i-s.size()+1];

        for (int j = 0; j < res.size(); j++)
        {
            dp[i] = (dp[i] - dp[i-s.size()+res[j]]) % mod;
        }
        for (int j = 0; j <= i-s.size(); j++)
            dp[i] = (dp[i] - dp[j]*mult[i-s.size()-j]) % mod;
        
        dp[i] = (dp[i] + mod) % mod;

        //cout << i << ": " << dp[i] << endl;
    }

    int result = 0;
    int multiple = 1;
    for (int i = n-1; i >= 0; i--)
    {
        result += dp[i] * multiple;
        multiple *= 26;

        multiple %= mod;
        result %= mod;
    }
 
    cout << result;

}
 
signed main() {
    //cin.tie(0);
    //ios_base::sync_with_stdio(false);
    int t = 1;
    //ifstream f("testcase.txt");
    //cin.rdbuf(f.rdbuf());
    //cin >> t;
    while (t--) { solve(); }
}

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

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED