【luogu P1955 [NOI2015]程序自动分析】 题解

题目链接：https://www.luogu.org/problemnew/show/P1955

并查集操作，1e9要离散化，数组要开大一些，操作前先执行合并操作

样例好毒啊（全是排好序的）

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
const int maxn = 100010;
int fa[maxn], n, flag, T, b[maxn];
struct node{
	int x, y, e;
}a[maxn];
bool cmp(node a, node b)
{
	return a.e > b.e;
}
int find(int x)
{
	return fa[x] == x ? x : fa[x] = find(fa[x]);
}
void init(int n)
{
	for(int i = 1; i <= n; i++) fa[i] = i;
}
int main()
{
	scanf("%d",&T);
	while(T--)
	{
		int tot = 0;
		memset(a, 0, sizeof(a));
		memset(b, 0, sizeof(b));
		memset(fa, 0, sizeof(fa));
		scanf("%d",&n);
		
		for(int i = 1; i <= n; i++) 
		{
			scanf("%d%d%d",&a[i].x,&a[i].y,&a[i].e);
			b[++tot] = a[i].x;
			b[++tot] = a[i].y;
		}
		sort(b + 1, b + 1 + tot);
		int m = unique(b + 1, b + 1 + tot) - b;
		for(int i = 1; i <= n; i++)
		{
			a[i].x = lower_bound(b + 1, b + 1 + m, a[i].x) - b;
			a[i].y = lower_bound(b + 1, b + 1 + m, a[i].y) - b;
		}
		init(m);
		sort(a+1, a+1+n, cmp);
		
		for(int i = 1; i <= n; i++)
		{
			flag = 1;
			int fx = find(a[i].x), fy = find(a[i].y);
			if(a[i].e == 1)
			{
				fa[fx] = fy;
			}
			else
			{
				if(fx == fy) 
				{
					printf("NO\n");
					flag = 0;
					break;
				}
			}
		}
		if(flag) printf("YES\n");
	}
	return 0;
}