hdu1331记忆化搜索

题目链接：点击打开链接

题意：求给的公式。

思路：记忆化搜索，暴力跑出来

#include <iostream>#include<cstdio>#include<cstring>using namespace std;const int maxn=20+2;int d[maxn][maxn][maxn],vis[maxn][maxn][maxn];int w(int a,int b,int c){   if(a<=0||b<=0||c<=0)return 1;    if(a>20||b>20||c>20)return w(20,20,20);if(vis[a][b][c])return d[a][b][c];     vis[a][b][c]=1;     if(a<b&&b<c)d[a][b][c]=w(a, b, c-1)+w(a, b-1, c-1)-w(a, b-1, c);else  d[a][b][c]=w(a-1, b, c)+ w(a-1, b-1, c)+w(a-1, b, c-1)-w(a-1, b-1, c-1); return d[a][b][c];}int main(){    int n,m,c,b,a,cunt,i;    memset(d,0,sizeof(d));    memset(vis,0,sizeof(vis));   while(~scanf("%d %d %d",&a,&b,&c))   {       if(a==-1&&b==-1&&c==-1)break;        printf("w(%d, %d, %d) = %d\n",a,b,c,w(a,b,c));   }    return 0;}