题解·连续攻击游戏

@luogu
看上去这是一道二分图题，将点i和它的两个属性值分别作为两个点集，分别连边后跑匈牙利树，若找不到匹配则输出解。

#include<cstdio>
#include<cstring>
#include<vector>
using namespace std;

vector<int> e[2000010];
int ans,n,x,y,cx[2000010],cy[2000010];
bool vis[2000010];

bool dfs(int u){
	for(unsigned int i=0;i<e[u].size();i++) {
		int v=e[u][i];
		if(!vis[v]) {
			vis[v]=1;
			if(cy[v]==-1||dfs(cy[v])){
				cx[u]=v;cy[v]=u;
				return true;
			}
		}
	}
	return false;
}

int main() {
	freopen("attack.in","r",stdin);
	freopen("attack.out","w",stdout);
	scanf("%d",&n);
	for(int i=1;i<=n;i++) {
		scanf("%d%d",&x,&y);
		e[x].push_back(i);
		e[y].push_back(i);
		//e[n+x].push_back(i);
		//e[n+y].push_back(i);
	}
	memset(cx,-1,sizeof cx);
	memset(cy,-1,sizeof cy);
	for(int i=1;i<=10000;i++)
		if(cx[i]==-1) {
			memset(vis,0,sizeof vis);
			if (!dfs(i)) {
				printf("%d\n",i-1);
				return 0;
			}
		}
	return 0;
}