제출 #44482

#	제출 시각UTC-0	아이디	문제	언어	결과	실행 시간	메모리
44482	2018-04-02 10:22:43	aome	Tents (JOI18_tents)	C++17	100 / 100	200 ms	35968 KiB

tents

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
#include <bits/stdc++.h>
using namespace std;
const int N = 3005;
const int mod = 1e9 + 7;
int n, m, f[N][N];
void add(int &x, int y) {
  x += x + y >= mod ? y - mod : y;
}
int main() {
  cin >> n >> m;
  f[n][m] = 1;
  for (int i = n; i >= 0; --i) {
    for (int j = m; j >= 0; --j) {
      if (j) {
        add(f[i][j - 1], f[i][j]);
        if (i) add(f[i - 1][j - 1], 4LL * f[i][j] * i % mod);
        if (i > 1) {
          add(f[i - 2][j - 1], 1LL * f[i][j] * i * (i - 1) / 2 % mod);
        }
        if (i && j > 1) {
          add(f[i - 1][j - 2], 1LL * f[i][j] * i * (j - 1) % mod);
        }
      }
      else if (i) add(f[i - 1][j], f[i][j]);
    }
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

• Subtask 1: 48 / 48
• Subtask 2: 52 / 52