Submission #120707

#	Time	Username	Problem	Language	Result	Execution time	Memory
120707		_demon_	Duathlon (APIO18_duathlon)	C++14	0 / 100	1146 ms	1048576 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll n,m;
ll child[100009];
ll ans;
ll w[100009];
vector<ll>v[100009];
void dfs1(int node,int p){
    child[node]=1;
    if(node!=p)w[node]=w[p]+1;
    for(int i=0;i<v[node].size();i++){
        int u=v[node][i];
        if(u==p)continue;
        dfs1(u,node);
        child[node]+=child[u];
    }
}
int a[100009];
void dfs2(int node,int p){
    ll sum=0;
    for(int i=0;i<v[node].size();i++){
        int u=v[node][i];
        if(w[u]>w[node]){
            sum+=child[u]*(n-child[u]-1);
        }
        else{
            sum+=(n-child[node])*(child[node]-1);
        }
    }
    a[node]=sum;
    ans+=sum;
    for(int i=0;i<v[node].size();i++){
        int u=v[node][i];
        if(u==p)continue;
        dfs2(u,node);
    }
}
int main(){
    cin>>n>>m;
    for(int i=0;i<m;i++){
        int a,b;
        cin>>a>>b;
        a--;b--;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    dfs1(0,0);
//  for(int i=0;i<n;i++)cout<<w[i]<<" ";
//  cout<<endl;
    dfs2(0,0);
//  for(int i=0;i<n;i++)cout<<a[i]<<" ";
//  cout<<endl;
    cout<<ans<<endl;
}

Compilation message (stderr)

count_triplets.cpp: In function 'void dfs1(int, int)':
count_triplets.cpp:12:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<v[node].size();i++){
                 ~^~~~~~~~~~~~~~~
count_triplets.cpp: In function 'void dfs2(int, int)':
count_triplets.cpp:22:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<v[node].size();i++){
                 ~^~~~~~~~~~~~~~~
count_triplets.cpp:33:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<v[node].size();i++){
                 ~^~~~~~~~~~~~~~~

• 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