POJ1579-记忆化搜索

#include<stdio.h>int a1[22][22][22]={0};//初始化为零 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 a1[20][20][20]=w(20,20,20);    if(a1[a][b][c])return a1[a][b][c];//记忆化搜索的关键     if(a<b&&b<c)    return a1[a][b][c]=w(a,b,c-1)+w(a,b-1,c-1)-w(a,b-1,c);    return a1[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); }    int main(){    int a,b,c,tem;    while(scanf("%d %d %d",&a,&b,&c),a!=-1||b!=-1||c!=-1){        tem=w(a,b,c);        printf("w(%d, %d, %d) = %d\n",a,b,c,tem);    }    //system("pause");    return 0;}