hdu 4739 Zhuge Liang's Mines

#include<iostream>
#include<cstring>
#include<cstdio>
#include<vector>
#include<algorithm>
using namespace std;
struct node{
    int x,y;
}a[22];
vector <int> mine;
int dp[(1<<20)+2];
int n;
bool cmp(node a,node b){
    if(a.x==b.x)
        return a.y<b.y;
    else
        return a.x<b.x;
}
void check(){
    int i,j,k,l;
    for(k=0;k<n;k++)
        for(i=k+1;i<n;i++)
            for(l=i+1;l<n;l++)
                for(j=l+1;j<n;j++)
                    if(a[i].x==a[k].x&&a[j].x==a[l].x&&a[i].y==a[j].y&&a[k].y==a[l].y&&(a[j].x-a[i].x==a[i].y-a[k].y))
                        mine.push_back((1<<i)|(1<<j)|(1<<k)|(1<<l));
}
int main(){
    while(scanf("%d",&n)&&n!=-1){
        int i,j;
        for(i=0;i<n;i++)
            scanf("%d%d",&a[i].x,&a[i].y);
        sort(a,a+n,cmp);
        mine.clear();
        check();
        memset(dp,0,sizeof(dp));
        for(i=0;i<(int)mine.size();i++)
            for(j=mine[i];j<=(1<<n)-1;j++)   //無需倒序
                if((j&mine[i])==mine[i]){
                    dp[j]=max(dp[j],dp[j-mine[i]]+4);
                }
        printf("%d\n",dp[(1<<n)-1]);
    }
    return 0;
}