（水题）洛谷

https://www.luogu.org/problemnew/show/P1464

#include<bits/stdc++.h>
using namespace std;
#define ll long long

ll a,b,c;

map<ll,int> m;

int dfs(ll a,ll b,ll c){
    if(a<=0||b<=0||c<=0)
        return 1;
    if(a>20||b>20||c>20)
        return dfs(20,20,20);
    ll p=10000*a+100*b+c;
    if(m.count(p))
        return m[p];
    else if(a<b&&b<c){
        int t=dfs(a,b,c-1)+dfs(a,b-1,c-1)-dfs(a,b-1,c);;
        m[p]=t;
        return t;
    }
    else{
        int t=dfs(a-1,b,c)+dfs(a-1,b-1,c)+dfs(a-1,b,c-1)-dfs(a-1,b-1,c-1);
        m[p]=t;
        return t;
    }
}

int main(){
    while(cin>>a>>b>>c){
        if(a==-1&&b==-1&&c==-1)
            return 0;
        else{
            printf("w(%lld, %lld, %lld) = %d
",a,b,c,dfs(a,b,c));
        }
    }
}