题目大意：有$n(n\leqslant10^6)$个变量，有若干限制，形如$x_l$与$x_r$必须相等或不相等，问是否有解

题解：并查集，把相同的塞在一个集合里，最后判一下不相等的是否在一个集合内，是则无解

卡点：当成了元素非$0$即$1$

 

C++ Code：

#include 
     
      #include 
      
       #define maxn 1000010int Tim, n, tot;int v[maxn << 1], f[maxn], l[maxn], r[maxn], e[maxn];int find(int x) { return x == f[x] ? x : (f[x] = find(f[x])); }inline void merge(int a, int b) { f[find(a)] = find(b); }int main() {	scanf("%d", &Tim);	while (Tim --> 0) {		scanf("%d", &n); tot = 0;		for (int i = 0; i < n; ++i) {			scanf("%d%d%d", l + i, r + i, e + i);			v[tot++] = l[i], v[tot++] = r[i];		}		tot = (std::sort(v, v + tot), std::unique(v, v + tot) - v);		for (int i = 0; i < tot; ++i) f[i] = i;		for (int i = 0; i < n; ++i) {			l[i] = std::lower_bound(v, v + tot, l[i]) - v;			r[i] = std::lower_bound(v, v + tot, r[i]) - v;			if (e[i]) merge(l[i], r[i]);		}		bool check = true;		for (int i = 0; i < n; ++i) if (!e[i]) check &= find(l[i]) != find(r[i]);		puts(check ? "YES" : "NO");	}	return 0;}