[NOI2015] 程序自动分析

代码

#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
inline int read(){
	int x=0,f=1;char c=getchar();
	while ('0'>c||c>'9') {if (c=='-') f=-1;c=getchar();}
	while ('0'<=c&&c<='9') x=(x<<1)+(x<<3)+(c^48),c=getchar();
	return x*f;
}
const int maxn(1e6+5);
int n,flag;
int f[maxn];
int cnt;
struct node{
	int x,y,z;
	bool operator < (const node& x) const{
		return z>x.z;
	}
}e[maxn];
int b[maxn*3];
inline int find(int x){
	return f[x]==x?x:f[x]=find(f[x]);
}

void init(){
	n=read();
	memset(e,0,sizeof(e));
	memset(b,0,sizeof(b));
	memset(f,0,sizeof(f));
	flag=1;
	cnt=0;
	for (int i(1);i<=n;++i){
		e[i].x=read(),e[i].y=read(),e[i].z=read();
		b[++cnt]=e[i].x;
		b[++cnt]=e[i].y;
	}
	sort(b+1,b+cnt+1);
	cnt=unique(b+1,b+cnt+1)-b-1;
	for (int i(1);i<=n;++i){
		e[i].x=lower_bound(b,b+cnt,e[i].x)-b;
		e[i].y=lower_bound(b,b+cnt,e[i].y)-b;
	}
	for (int i(1);i<=cnt;++i) f[i]=i;
	sort(e+1,e+1+n);
}

void doit(){
	for (int i(1);i<=n;++i){
		int x=find(e[i].x),y=find(e[i].y);
		if (e[i].z) f[x]=y;
		else if (x==y){
			puts("NO");
			flag=0;
			break;
		}
	}
	if (flag) puts("YES");
}

int main(){
	int t=read();
	while (t--){
		init();
		doit();
	}
	return 0;
}