Submission #51166760

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Source Code Expand

/*
  Author: Denys Smirnov
  Time: 2024-03-12 00:23:36
*/

#include "bits/stdc++.h"
#include "atcoder/modint.hpp"

#ifdef DENDI239
#define D                                                                      \
  for (bool _flag_dendi239 = true; _flag_dendi239; _flag_dendi239 = false)
#else
#define D while (false)
#endif

using namespace std;
using Mint = atcoder::modint998244353;

Mint F(int n, Mint m) {
  if (n == 1)
    return 0;
  // else if (n == 2)
  //   return m * (m - 1);
  // else
  //   return m * (m - 1).pow(n - 1) - F(n - 1, m);

  //  m-1^n-1 - m-1^n-2 + ... +- m-1   | * (m-1 + 1)
  //  m-1^n + m-1^n-1 -m-1^n-1 - m-1^n-2 + ... +- m-1^2 +- m-1
  //          -------  -------   -------          -----
  //  m-1^n +- m-1
  //  m-1(m-1^n-1 +- 1) / m

  return (m - 1) * (m.pow(n - 1) - Mint(-1).pow(n - 1));
}

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int n, m_int;
  cin >> n >> m_int;

  Mint m(m_int);
  
  if (n == 1) {
    cout << m.val() << "\n";
    return 0;
  }

  Mint res = 0;
  for (size_t i = 0; i + 1 < n; ++i) {
    if (i % 2) {
      res -= m * (m - 1).pow(n - 1 - i);
    } else {
      res += m * (m - 1).pow(n - 1 - i);
    }
  }

  cout << res.val() << "\n";
}

Submission Info

Compile Error

Main.cpp: In function ‘int main()’:
Main.cpp:51:28: warning: comparison of integer expressions of different signedness: ‘size_t’ {aka ‘long unsigned int’} and ‘int’ [-Wsign-compare]
   51 |   for (size_t i = 0; i + 1 < n; ++i) {
      |                      ~~~~~~^~~

Judge Result