Submission #115868

#	Time	Username	Problem	Language	Result	Execution time	Memory
115868		zubec	Duathlon (APIO18_duathlon)	C++14	100 / 100	262 ms	27424 KiB

count_triplets

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

const int N = 200100;

vector <int> g[N];

vector <int> stck;

vector <vector <int> > cmp;

int tin[N], fup[N], tim, n;

bool used[N];

void findCutpoints(int v, int p){
    used[v] = 1;
    tin[v] = fup[v] = ++tim;
    stck.push_back(v);
    for (int i = 0; i < g[v].size(); i++){
        int to = g[v][i];
        if (to == p)
            continue;
        if (!used[to]){
            findCutpoints(to, v);
            fup[v] = min(fup[v], fup[to]);
            if (tin[v] <= fup[to]){
                cmp.push_back({v});
                while(cmp.back().back() != to){
                    cmp.back().push_back(stck.back());
                    stck.pop_back();
                }
            }
        } else {
            fup[v] = min(fup[v], tin[to]);
        }
    }
}

ll ans = 0;

int sz[N];

void dfs1(int v, int p){
    sz[v] = v <= n;
    used[v] = 1;
    for (int i = 0; i < g[v].size(); i++){
        int to = g[v][i];
        if (to == p)
            continue;
        dfs1(to, v);
        sz[v] += sz[to];
    }
}

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

int main(){
    ios_base::sync_with_stdio(0);cin.tie(0);
    int m;
    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]){
            findCutpoints(i, 0);
            if (!stck.empty()){
                cmp.push_back(stck);
                stck.clear();
            }
        }
    }
    memset(used, 0, sizeof(used));
    for (int i = 1; i <= n; i++)
        g[i].clear();
    for (int i = 0; i < cmp.size(); i++){
        for (int j = 0; j < cmp[i].size(); j++){
            int v = cmp[i][j];
            g[v].push_back(n+i+1);
            g[n+i+1].push_back(v);
        }
    }
    for (int i = 1; i <= n; i++){
        if (!used[i]){
            dfs1(i, 0);
            ans += (sz[i])*1ll*(sz[i]-1)*(sz[i]-2);
            dfs2(i, 0, sz[i]);
        }
    }

    cout << ans;

}

Compilation message (stderr)

count_triplets.cpp: In function 'void findCutpoints(int, int)':
count_triplets.cpp:22:23: 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 dfs1(int, int)':
count_triplets.cpp:49:23: 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, ll)':
count_triplets.cpp:60:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < g[v].size(); i++){
                         ~~^~~~~~~~~~~~~
count_triplets.cpp:74:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < g[v].size(); i++){
                     ~~^~~~~~~~~~~~~
count_triplets.cpp: In function 'int main()':
count_triplets.cpp:105:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < cmp.size(); i++){
                     ~~^~~~~~~~~~~~
count_triplets.cpp:106:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int j = 0; j < cmp[i].size(); j++){
                         ~~^~~~~~~~~~~~~~~

• 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