POJ 1597 Function Run Fun

记忆化搜索。

#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
#include<map>
#include<queue>
#include<string>
#include<iostream>
using namespace std;

struct X{
    int x,y,z;
    X(int xx,int yy,int zz)
    {
        x=xx;
        y=yy;
        z=zz;
    }
    bool operator < (const X &a) const {
        if(x!=a.x) return x>a.x;
        if(y!=a.y) return y>a.y;
        return z>a.z;
    }
};
int a,b,c;
map<X,bool>f;
map<X,int>w;

int work(int x,int y,int z)
{
    if(f[X(x,y,z)]) return w[X(x,y,z)];
    
    f[X(x,y,z)]=true;
    if(x <= 0 || y <= 0 || z <= 0) w[X(x,y,z)]=1;
    else if(x > 20 || y > 20 || z > 20) w[X(x,y,z)] = work(20,20,20);
    else if(a < b && b < c) w[X(x,y,z)] =work(x, y, z-1) + work(x, y-1, z-1) - work(x, y-1, z);
    else w[X(x,y,z)] = work(x-1, y, z) + work(x-1, y-1, z) + work(x-1, y, z-1) - work(x-1, y-1, z-1);
    
    return w[X(x,y,z)];
}

int main()
{
    while(~scanf("%d%d%d",&a,&b,&c))
    {
        if(a==-1&&b==-1&&c==-1) break;
        printf("w(%d, %d, %d) = %d
",a,b,c,work(a,b,c));
    }
    
    return 0;
}