Author: lllyouo
Date: 20250422
tag: tarjan、割点
link: https://www.acwing.com/problem/content/365/

问题描述

link

分析

略

参考代码

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

const int N = 1e5 + 10, M = 5e5 + 10;
int h[N], e[M * 2], ne[M * 2], idx;
int dfn[N], low[N], num;
bool cut[N];
long long ans[N], sz[N];
int n, m, root;

void add(int a, int b) {
    e[idx] = b, ne[idx] = h[a], h[a] = idx++;
}

void tarjan(int x) {
    dfn[x] = low[x] = ++num;
    int child = 0;
    sz[x] = 1;
    long long sum = 0, sum_s = 0;
    for (int i = h[x]; i != -1; i = ne[i]) {
        int y = e[i];
        if (!dfn[y]) {
            tarjan(y);
            sz[x] += sz[y];
            low[x] = min(low[x], low[y]);
            if (low[y] >= dfn[x]) {
                child++;
                if (x != root || child > 1) cut[x] = true;
                sum += sz[y] * (n - sz[y]);
                sum_s += sz[y];
            }
        } else low[x] = min(low[x], dfn[y]);
    }
    
    if (cut[x]) ans[x] = sum + (n - 1) + (n - 1 - sum_s) * (1 + sum_s);
    else ans[x] = 2 * (n - 1);
}

int main() {
    cin >> n >> m;
    memset(h, -1, sizeof h);
    for (int i = 0; i < m; i++) {
        int a, b; cin >> a >> b;
        add(a, b), add(b, a);
    }
    
    tarjan(1);

    for (int i = 1; i <= n; i++) cout << ans[i] << endl;
    
    return 0;
}