Submission #104527

#	Time	Username	Problem	Language	Result	Execution time	Memory
104527		_demon_	Duathlon (APIO18_duathlon)	C++14	0 / 100	135 ms	11896 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;
int n,m;
vector<int>v[100009];
int child1[100009];
int child2[100009];
void dfs(int node,int p){
    for(int i=0;i<v[node].size();i++){
        int u=v[node][i];
        if(u==p) continue;
        dfs(u,node);
        child1[node]=child1[u]+1;
    }   
}
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);
    }
    int r;
    for(int i=0;i<n;i++){
        if(v[i].size()==1){r=i;break;}
    }dfs(r,r);
    for(int i=0;i<n;i++){
        child2[i]=n-child1[i]-1;}
    long long ans=0;for(int i=0;i<n;i++){int x=child1[i]*(child1[i]-1)/2;int y=child2[i]*(child2[i]-1)/2;ans+=x+y;}cout<<ans<<endl;
}

Compilation message (stderr)

count_triplets.cpp: In function 'void dfs(int, int)':
count_triplets.cpp:8:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<v[node].size();i++){
                 ~^~~~~~~~~~~~~~~
count_triplets.cpp: In function 'int main()':
count_triplets.cpp:27:9: warning: 'r' may be used uninitialized in this function [-Wmaybe-uninitialized]
     }dfs(r,r);
      ~~~^~~~~

• 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