HDU-1331 Function Run Fun （记忆化搜索）

这里写图片描述

最简单的记忆化搜索，题目有点问题，a, b, c中若既满足其中一个不大于0，又满足其中一个大于20，按前一种情况。

Code:

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 int w[21][21][21];
 4 
 5 int dfs(int a, int b, int c) {
 6     if (a <= 0 || b <= 0 || c <= 0) return 1;
 7     if (~w[a][b][c]) return w[a][b][c]; 
 8     if (a < b && b < c) return w[a][b][c] = dfs(a, b, c-1) + dfs(a, b-1, c-1) - dfs(a, b-1, c);
 9     else return w[a][b][c] = dfs(a-1, b, c) + dfs(a-1, b-1, c) + dfs(a-1, b, c-1) - dfs(a-1, b-1, c-1);
10 }
11 
12 int main() {
13     int a, b, c, ans;
14     memset(w, -1, sizeof(w));
15     while(~scanf("%d%d%d", &a, &b, &c)) {
16         if (a == -1 && b == -1 && c == -1) break;
17         if (a <= 0 || b <= 0 || c <= 0) ans = 1;
18         else if (a > 20 || b > 20 || c > 20) ans = dfs(20, 20, 20);
19         else ans = dfs(a, b, c);
20         printf("w(%d, %d, %d) = %d
", a, b, c, ans);
21     }
22 
23     return 0;
24 }