Submission #261064

#	Time	Username	Problem	Language	Result	Execution time	Memory
261064		Hideo	Duathlon (APIO18_duathlon)	C++17	23 / 100	104 ms	14072 KiB

count_triplets

//1610612741, 1000000007
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
//#pragma GCC optimization ("O3")
//#pragma GCC optimization ("unroll-loops")
//#pragma GCC optimize ("Ofast")
//#pragma GCC target ("avx,avx2,fma")

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

#define all(s) s.begin(), s.end()
#define ok puts("ok")
#define ll long long
#define pb push_back
#define mk make_pair
#define fr first
#define sc second
#define vi vector < int >
#define pi pair < int, int >
#define pii pair < int, pi >
#define next next123
#define left left123

const int N = 2e5 + 7;
const int INF = 1e9 + 7;

ll S1, S2, S3;
int h[N], sz[N];
int n, m;

vi g[N];

void precalc (int v, int p = 0){
    h[v] = h[p] + 1;
    sz[v] = 1;
    for (int to : g[v]){
        if (!h[to]){
            precalc(to, v);
            sz[v] += sz[to];
        }
    }
}

void calc1 (int v, int csz){
    for (int to : g[v])
        if (h[to] - h[v] == 1)
            S1 += 1LL * (csz - sz[to] - 1) * sz[to];
    S1 += 1LL * (csz - sz[v]) * (sz[v] - 1);
    for (int to : g[v])
        if (h[to] - h[v] == 1)
            calc1(to, csz);
}

main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin >> n >> m;
    for (int i = 1; i <= m; i++){
        int a, b;
        cin >> a >> b;
        g[a].pb(b);
        g[b].pb(a);
    }
    for (int i = 1; i <= n; i++)
        if (!h[i])
            precalc(i);
    for (int i = 1; i <= n; i++)
        if (h[i] == 1)
            calc1(i, sz[i]);
    cout << S1;
}

Compilation message (stderr)

count_triplets.cpp:54:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main(){
      ^

• 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