并查集进阶版

过关代码如下

#define _CRT_SECURE_NO_WARNINGS
#include<bits/stdc++.h>
#include<unordered_set>
using namespace std;

int n, m;
vector<int> edg[400005];
int a[400005], be[400005]; // a的作用就是存放要摧毁
int k;
int fa[400005];
int daan[400005];

void add(int x, int y) {
	edg[x].push_back(y);
	edg[y].push_back(x);
}

int find(int x) {
	if (x == fa[x]) return x;
	return fa[x] = find(fa[x]);
}

void uni(int x, int y) {
	int xx = find(x), yy = find(y);
	if (xx == yy) return;
	fa[xx] = yy;
}

int main() {
	cin >> n >> m;
	int l, r;
	for (int i = 1; i <= m; i++) {
		cin >> l >> r;
		add(l, r); // 建立边
	}
	cin >> k;
	for (int i = 1; i <= k; i++) {
		cin >> a[i];
		be[a[i]] = 1; // 标记为1，表示被摧毁
	}
	int ans = n-k; // 一开始的时候每个点都是一个块
	// 初始化并查集
	for (int i = 0; i <= n; i++) fa[i] = i;
	// 开始区分联通分量
	for (int i = 0; i < n; i++) {
		if (be[i]) continue;
		for (int u : edg[i]) {
			if (be[u]) continue;
			if (find(i) == find(u)) continue;
			uni(i, u);// 连接
			ans--;
		}
	}
	daan[k+1] = ans;
	for (int i = k; i >= 1; i--) {
		//cout << "yes" << endl;
		int xiufu = a[i];
		ans++;
		be[xiufu] = 0;  // 恢复为1
		for (int u : edg[xiufu]) {
			if (be[u]) continue;
			if (find(u) == find(xiufu)) continue;
			ans--;
			uni(u, xiufu);
		}
		daan[i] = ans;
	}
	for (int i = 1; i <= k+1; i++) {
		cout << daan[i] << endl;
	}
	//cout << " now";
	return 0;
}