hdu 4739 Zhuge Liang's Mines 状态压缩

[code]#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
#define maxn 55
#define maxm 1200000
int cnt, dp[maxm];

struct point{
    int x, y;
}p[maxn];

struct square{
    int a, b, c, d;
    void Set(int a1, int b1, int c1, int d1) {
        a = a1, b = b1, c = c1, d = d1;
    }
}S[maxn];

int cmp(point a, point b) {
    if(a.x == b.x)
        return a.y < b.y;
    else
        return a.x < b.x;
}

int dfs(int s) {

    if(dp[s] != -1)
        return dp[s];

    int Max = 0;
    for(int i = 0; i < cnt; i++) {
        if( (s & (1 << S[i].a)) + ( s & (1 << S[i].b)) + (s & (1 << S[i].c)) + (s & (1 << S[i].d)) == 0) {
            int st = s + (1 << S[i].a) +(1 << S[i].b) + (1 << S[i].c) + (1 << S[i].d) ;
            Max = max(Max,dfs(st) + 4);
        } 
    }
    return dp[s] = Max;
}

int main() {
    int n;
    while(scanf("%d", &n) == 1 ) {
        if(n == -1)
            break;
        for(int i = 0; i < n; i++)
            scanf("%d%d", &p[i].x, &p[i].y);
        sort(p,p+n,cmp);
        cnt = 0;
        for(int i = 0; i < n; i++)
            for(int j = i + 1; j < n; j++) {
                if(p[i].x != p[j].x)
                    break;
                for(int k = j + 1; k < n; k++)
                    for(int l = k + 1; l < n; l++) {
                        if(p[k].x != p[l].x)
                            continue;
                        if( p[i].y == p[k].y && p[j].y == p[l].y && p[j].y - p[i].y == p[k].x - p[i].x) {
                            S[cnt++].Set(i,j,k,l);
                        }
                    }
            }
        memset(dp,-1,sizeof(dp));
        printf("%d\n",dfs(0));
    }
    return 0;
}