赛码网 5.12周考

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long ll;
 4 typedef pair<int, int> pii;
 5 const int maxn = 1e5 + 10;
 6 
 7 ll dp[110][110][110];
 8 int n, m;
 9 void add(ll &x, ll y) {
10     x += y;
11 }
12 void solve() {
13     cin >> n >> m;
14     dp[0][0][0] = 1;
15     for (int i = 1; i <= n; i++) {
16         for (int j = 0; j <= m; j++) {
17             for (int k = 0; k <= m - j; k++) {
18                 ll cur = dp[i - 1][j][k];
19                 add(dp[i][j][k], cur); //1
20                 if(j + 1 <= m)
21                     add(dp[i][j + 1][k], cur * (m - j - k));//2
22                 if(j >= 1)
23                     add(dp[i][j - 1][k + 1], cur * j);//3
24                 //if(k + 1 <= m)
25                     //add(dp[i][j][k + 1], cur * (m - j - k));
26                 if(j + 2 <= m)
27                     add(dp[i][j + 2][k], cur * (m - j - k) * (m - j - k - 1) / 2);//4
28                 if(k + 1 <= m)
29                     add(dp[i][j][k + 1], cur * j * (m - j - k));
30                 if(j >= 2)
31                     add(dp[i][j - 2][k + 2], cur * j * (j - 1) / 2);
32             }
33         }
34     }
35     ll res = 0;
36     for (int i = 0; i <= m; i++) {
37         for (int j = 0; j <= m - i; j++)
38             add(res, dp[n][i][j]);
39     }
40     cout << res << endl;
41 }
42 
43 int main() {
44     freopen("test.in", "r", stdin);
45     solve();
46     return 0;
47 }