Function Run Fun POJ - 1579

​​原题链接​​

考察:记忆化搜索

思路:

        可用递推和记忆化搜索两种方式.

1 #include <iostream>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <cstdio>
 5 using namespace std;
 6 const int N = 21;
 7 int f[N][N][N];
 8 int dfs(int a,int b,int c)
 9 { 
10     if(a<=0||b<=0||c<=0) return 1;
11     else if(a>20||b>20||c>20) return dfs(20,20,20);
12     if(f[a][b][c]!=-1) return f[a][b][c];
13     if(a<b&&b<c)
14       return f[a][b][c] = dfs(a, b, c - 1) + dfs(a, b - 1, c - 1) - dfs(a, b - 1, c);
15     else 
16       return f[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);
17 }
18 int main() 
19 {
20     int a,b,c;
21     memset(f,-1,sizeof f);
22     while(scanf("%d%d%d",&a,&b,&c)!=EOF&&(a!=-1||b!=-1||c!=-1))
23         printf("w(%d, %d, %d) = %d\n",a,b,c,dfs(a,b,c));
24     return 0;
25 }

记忆化搜索

1 #include <iostream>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <cstdio>
 5 using namespace std;
 6 const int N = 21;
 7 int f[N][N][N];
 8 int main() 
 9 {
10     int a,b,c;
11     for(int i=0;i<=20;i++)
12       for(int j=0;j<=20;j++)
13         for(int k=0;k<=20;k++)
14             f[i][j][k] = 1;
15     for(int i=1;i<=20;i++)
16       for(int j=1;j<=20;j++)
17         for(int k=1;k<=20;k++)
18         {
19             if(i<j&&j<k) f[i][j][k] = f[i][j][k-1]+f[i][j-1][k-1]-f[i][j-1][k];
20             else f[i][j][k] = f[i-1][j][k]+f[i-1][j-1][k]+f[i-1][j][k-1]-f[i-1][j-1][k-1];
21         }
22     while(scanf("%d%d%d",&a,&b,&c)!=EOF&&(a!=-1||b!=-1||c!=-1))
23     {
24         int ta = a,tb = b,tc = c;
25         if(a<0||b<0||c<0) a = 0,b = 0,c = 0;
26         else if(a>20||b>20||c>20) a= 20,b = 20,c =20;
27         printf("w(%d, %d, %d) = %d\n",ta,tb,tc,f[a][b][c]);
28     }
29     return 0;
30 }

递推

 

几个月前做过这道题,当时不会写来着,那时真的连算法门都没入.

​​P1464 Function​​ 双倍经验