Submission #370728

#	Time	Username	Problem	Language	Result	Execution time	Memory
370728		Leonardo_Paes	Duathlon (APIO18_duathlon)	C++17	31 / 100	234 ms	26904 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ar array
#define sz(a) ((int)(a).size())
#define all(a) (a).begin(),(a).end()
typedef pair<int,int> pii;
#define f first
#define s second
const int maxn = 1e5+10;
vector<int> grafo[maxn], aux[maxn];
int n, m, dp[maxn], sz[maxn], qtd[maxn], qtd2[maxn], color[maxn], c;
bool instack[maxn], mark[maxn];
stack<int> s;
void compress(int u, int p = 0){
    instack[u] = mark[u] = 1;
    s.push(u);
    //cout << "entrei em " << u << endl;
    for(int v : grafo[u]){
        if(instack[v] and v != p){
            c++;
            int vv;
            do{
                vv = s.top();
                //cout << vv << endl;
                color[vv] = c;
                instack[vv] = 0;
                s.pop();
            }while(vv != v);
        }
        if(!mark[v]) compress(v, u);
    }
    if(instack[u]) s.pop();
    instack[u] = 0;
}
int solve(int u, int p = 0){ // lca of path is u, 1 as a root
    int ans = qtd[u]*(qtd[u]-1)*(qtd[u]-2)/2; // sum of dps
    sz[u] = qtd[u];
    for(int v : grafo[u]){
        if(v == p) continue;
        ans += solve(v, u);
        sz[u] += sz[v];
        qtd2[u] += qtd2[v] + sz[v] * qtd[u];
    }
    int qtdd = sz[u] - qtd[u];
    for(int v : grafo[u]){
        if(v == p) continue;
        qtdd -= sz[v];
        dp[u] += sz[v] * qtdd * qtd[u]; // 1 from each
        dp[u] += sz[v] * (qtd[u] * qtd[u] - 1) / 2;
        dp[u] += (sz[u] - sz[v]) * qtd2[v];
    }
    if(grafo[u].size() == 1){
        qtd2[u] = sz[u] - 1 + 2 * (sz[u] - 1) * (sz[u] - 2);
    }
    return ans + dp[u];
}
int32_t main(){
    ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
    cin >> n >> m;
    for(int i=1; i<=m; i++){
        int u, v;
        cin >> u >> v;
        grafo[u].push_back(v);
        grafo[v].push_back(u);
    }
    for(int i=1; i<=n; i++) aux[i] = grafo[i];
    for(int i=1; i<=n; i++) if(!mark[i]) compress(i);
    for(int i=1; i<=n; i++) grafo[i].clear();
    set<pair<int,int>> edges;
    for(int i=1; i<=n; i++){
        if(!color[i]) color[i] = ++c;
        qtd[color[i]]++;
    }
    for(int i=1; i<=n; i++){
        for(int e : aux[i]){
            int u = color[i], v = color[e];
            if(u > v) swap(u, v);
            if(u == v or edges.count({u, v})) continue;
            edges.insert({u, v});
            grafo[u].push_back(v);
            grafo[v].push_back(u);
        }
    }
    int ans = 0;
    for(int i=1; i<=c; i++){
        if(!sz[i]) ans += solve(i);
    }
    for(int i=1; i<=n; i++){
        //cout << color[i] << " " << qtd2[color[i]] << endl;
    }
    cout << 2*ans << "\n";
    /*
6 7
1 2
2 3
3 1
3 4
4 5
5 6
6 4
    */
    return 0;
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 8 / 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