Submission #603172

#	Time	Username	Problem	Language	Result	Execution time	Memory
603172		LunaMeme	Duathlon (APIO18_duathlon)	C++14	0 / 100	118 ms	14072 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;
typedef vector<int> vi;
typedef long long ll;
#define PB push_back
#define FOR(i, x, y) for (int i =x; i < y; i ++)
ll f(ll n){
    return (1LL * n * (n - 1) * (n - 2)) /3;
}
ll g(ll l){
    return 1LL * (l -1) * (l - 2);
}
ll ans = 0; int n, m;
const int MAXN = 1e5 + 5;
vi adj[MAXN];
int sz[MAXN], par[MAXN];
int find(int a){
    if (a == par[a]) return a;
    return par[a] = find(par[a]);
}
void onion(int a, int b){
    a = find(a); b = find(b);
    //cout << a << ' ' << b << '\n';
    if (a == b) return;
    if (sz[a] < sz[b]) swap(a, b);
    sz[a] += sz[b];
    sz[b] = 1;
    par[b] = par[a];
}
int dist[MAXN] = { -1 };
void dfs(int curr, int nodes){
    for (auto next : adj[curr]){
        if (dist[next] >= 0 && dist[next] ==  dist[curr] - 1) continue;
        //cout << curr << " -> " << next << '\n';
        if (dist[next] >= 0){//cycle
            int c_length = dist[curr] + 1 - dist[next];
            //cout << next << ' ' << c_length << '\n';
            ans += 2*f(c_length) + 1LL* (nodes- c_length)* g(c_length);
            dist[next] = dist[curr] + 1;
        }
        else{
            dist[next] = dist[curr] + 1;
            dfs(next, nodes);
        }
    }
}
int main(){
    cin >> n >> m;
    FOR(i, 1, n + 1){
        par[i] = i;
        sz[i] = 1;
    }
    FOR(i, 0, m){
        int a, b; cin >> a >> b;
        adj[a].PB(b);
        adj[b].PB(a);
        onion(a, b);
    }

    //bfs for each component
    int visited[MAXN]  = { 0 };
    memset(dist, -1, sizeof dist);
    FOR(i, 1, n+ 1){
        if (visited[find(i)])
            continue;
        int a = find(i);
        visited[a] = 1;
        ans += f(sz[a]);
        dist[i] = 0;  
        dfs(i, sz[a]);
    }
    cout << ans;
}

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