[HDU 4739]Zhuge Liang's Mines：状压DP

/*
User:Small
Language:C++
Problem No.:4739
*/
#include<bits/stdc++.h>
#define ll long long
#define inf 999999999
using namespace std;
int n,ans,dp[(1<<20)+5];
vector<int> g[25];
struct no{
int x,y;
bool operator<(const no b)const{
return x==b.x?y<b.y:x<b.x;
}
}p[25];
bool ok(int i,int j,int k,int l){
if(p[i].x!=p[j].x||p[i].y!=p[k].y||p[j].y!=p[l].y||p[k].x!=p[l].x) return 0;
if(abs(p[j].y-p[i].y)!=abs(p[k].x-p[i].x)) return 0;
return 1;
}
void solve(){
ans=0;
for(int i=1;i<=n;i++) g[i].clear();
memset(dp,0,sizeof(dp));
for(int i=1;i<=n;i++)
cin>>p[i].x>>p[i].y;
sort(p+1,p+n+1);
for(int a=1;a<=n;a++){
for(int b=a+1;b<=n;b++){
for(int c=b+1;c<=n;c++){
for(int d=c+1;d<=n;d++){
if(ok(a,b,c,d)){
int tmp=0;
tmp|=1<<(a-1);
tmp|=1<<(b-1);
tmp|=1<<(c-1);
tmp|=1<<(d-1);
g[a].push_back(tmp);
}
}
}
}
}
for(int i=0;i<(1<<n);i++){
for(int j=1;j<=n;j++){
if((i>>(j-1))&1){
for(int k=0;k<g[j].size();k++){
int t=g[j][k];
if((i|t)==i)
dp[i]=max(dp[i^t]+4,dp[i]);
}
}
}
}
cout<<dp[(1<<n)-1]<<endl;
}
int main(){
freopen("data.in","r",stdin);//
ios::sync_with_stdio(false);
while(cin>>n&&n!=-1) solve();
return 0;
}