Submission #698844

#	Time	Username	Problem	Language	Result	Execution time	Memory
698844		vjudge1	New Home (APIO18_new_home)	C++17	0 / 100	9 ms	14676 KiB

new_home

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

#define int long long
#define endl '\n'

const int M = 3e5+5, MOD = 1e9+7;
int d[M], noc[M], n, dp[M], vis[M], cnt = 1;
vector<int> node[M];

void dfs(int s, int p = 1) {
    noc[s]++;
    vis[s] = cnt;
    for (int i:node[s]) {
        if (!vis[i]) {
            d[i] = d[s]+1;
            dfs(i, s);
            noc[s] += noc[i];
        }
    }
}

void dfs2(int s, int p = 1) {
    vis[s] = cnt;
    for (int i:node[s]) {
        if (!vis[i]) {
            dp[i] = dp[s] + n - 2*noc[i];
            dfs2(i, s);
        }
    }
}

signed main() {
    cin.tie(0)->sync_with_stdio(0);

    int m;
    cin >> n >> m;

    for (int i = 1; i <= m; i++) {
        int a, b;
        cin >> a >> b;
        node[a].push_back(b);
        node[b].push_back(a);
    }

    int ans = 0;
    for (int i = 1; i <= n; i++) {
        if (!vis[i]) {
            dfs(i, i);
            for (int i = 1; i <= n; i++) dp[1] += d[i], vis[i] = (vis[i] == cnt?0:vis[i]);

            dfs2(i, i);
            for (int i = 1; i <= n; i++) ans += dp[i] - n + 1, ans %= MOD;
            cnt++;
        }
    }
    cout << ans << endl;

    return 0;
}
/*
4 3
1 2 2 3 3 4
*/

• Subtask 1: 0 / 5
• Subtask 2: 0 / 7
• Subtask 3: 0 / 10
• Subtask 4: 0 / 23
• Subtask 5: 0 / 35
• Subtask 6: 0 / 20