Submission #103640

#	Time	Username	Problem	Language	Result	Execution time	Memory
103640		zubec	Duathlon (APIO18_duathlon)	C++14	23 / 100	1163 ms	1049600 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;

const int N = 100100;

int n, m;

vector <int> g[N];

ll sz[N];

ll ans = 0;

bool used[N];

void dfs(int v, int p){
    sz[v] = 1;
    used[v] = 1;
    for (int i = 0; i < g[v].size(); i++){
        int to = g[v][i];
        if (to == p)
            continue;
        dfs(to, v);
        sz[v] += sz[to];
    }
}
void dfs2(int v, int p, int n){
    ll cursum = n-sz[v];
    for (int i = 0; i < g[v].size(); i++){
        int to = g[v][i];
        if (to == p)
            continue;
        dfs2(to, v, n);
        ans += cursum*sz[to]*2;
        cursum += sz[to];
    }
}

int main(){
    ios_base::sync_with_stdio(0);cin.tie(0);
    //freopen("input.txt", "r", stdin);freopen("output.txt", "w", stdout);

    cin >> n >> m;
    for (int i = 1; i <= m; i++){
        int u, v;
        cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    for (int i = 1; i <= n; i++){
        if (!used[i]){
            dfs(i, 0);
            dfs2(i, 0, sz[i]);
        }
    }
    cout << ans;

}

/**

4 3
1 2
2 3
3 4

5 4
1 2
3 4
4 5
4 1

*/

Compilation message (stderr)

count_triplets.cpp: In function 'void dfs(int, int)':
count_triplets.cpp:21:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < g[v].size(); i++){
                     ~~^~~~~~~~~~~~~
count_triplets.cpp: In function 'void dfs2(int, int, int)':
count_triplets.cpp:31:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < g[v].size(); i++){
                     ~~^~~~~~~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 8
• Subtask 4: 10 / 10
• Subtask 5: 13 / 13
• Subtask 6: 0 / 15
• Subtask 7: 0 / 20
• Subtask 8: 0 / 8
• Subtask 9: 0 / 10