Submission #997644

#	Time	Username	Problem	Language	Result	Execution time	Memory
997644		vjudge1	Duathlon (APIO18_duathlon)	C++17	100 / 100	63 ms	33252 KiB

count_triplets

#include <bits/stdc++.h>

#define ll long long
using namespace std;
const int N = 2e5 + 2;
ll ans  = 0;
int num[N + 2], low[N + 2], timer , n , m , scc;
stack < int > st;
vector < int > adj[N + 2] , g[N + 2];
ll sz[N + 2];
int mN;
void dfs(int u , int p = - 1){
    low[u] = num[u] = ++timer;
    st.push(u);
    for(auto v: adj[u]){
        if(v == p)continue;
        if(!num[v]){
            dfs(v , u);
            low[u] = min(low[u] , low[v]);
            if(low[v] >= num[u]){
                scc ++;
                g[scc].push_back(u);
                g[u].push_back(scc);
                int y;
                do{
                    y = st.top();
                    st.pop();
                    g[y].push_back(scc);
                    g[scc].push_back(y);
                }while(y !=  v);
            }
        }
        else{
            low[u] = min(low[u] , num[v]);
        }
    }
}

ll three_im(ll x , ll z){
    if(x < z)return 0;
    ll k = 1;
    for(ll i = x ;i >= x - z + 1; i --){
        k *= i;
    }
    return k ;
}
ll cal(ll f , ll k){
    return three_im(f , 2) * (k - 1);
}
void dfs2(int u , int p = - 1){
    if(u <= n)sz[u] ++;
    for(auto v: g[u]){
        if(v == p)continue;
        dfs2(v , u);
        sz[u] += sz[v];
    }
    if(u <= n)return ;
    ll oth = mN - sz[u] ;
    for(auto v: g[u]){
        if(v == p) continue;
        ans -= cal(sz[v] , g[u].size());
    }
    ans -= cal(oth , g[u].size());
}
void solve() {
    cin >> n >> m;
    scc = n;
    for(int i = 1; i <= m ; i ++){
        int u , v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    for(int i = 1; i <= n ; i++){
        if(!num[i]){
            mN = timer;
            dfs(i);
            mN = timer - mN;
            ans += three_im(mN, 3);
            dfs2(i);
        }
    }
    cout << ans;
}

signed main() {
    ios::sync_with_stdio(0), cin.tie(0);
    
    #define _ "minrect."
    if (fopen(_ "inp", "r")) {
        freopen(_ "inp", "r", stdin);
        freopen(_ "out", "w", stdout);
    }
    
    solve();
}

Compilation message (stderr)

count_triplets.cpp: In function 'int main()':
count_triplets.cpp:91:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   91 |         freopen(_ "inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
count_triplets.cpp:92:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   92 |         freopen(_ "out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

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