Submission #64941

#	Time	Username	Problem	Language	Result	Execution time	Memory
64941		gusfring	Duathlon (APIO18_duathlon)	C++14	49 / 100	59 ms	16392 KiB

count_triplets

#include<bits/stdc++.h>
#define ll long long
using namespace std;
#define pb push_back
const int N=100005,M=100005;

vector<int> g[N*2];
int hd[N],to[M],ne[M],num,n,m,siz[N*2];
int v[N],cnt,dc,dfn[N],low[N],nn;
ll ans=0;

struct lines{ int x,y;};
stack<lines> S;

inline void add(int x,int y){ to[++num]=y,ne[num]=hd[x],hd[x]=num;}

void tarjan(int x,int fa){
  dfn[x] = low[x] = ++dc, nn++;
  for(int i=hd[x]; i; i=ne[i]) if(to[i]!=fa)
    if(!dfn[to[i]]){
      S.push((lines){x,to[i]});
      tarjan(to[i],x), low[x] = min(low[x], low[to[i]]);
      if(low[to[i]] >= dfn[x]){
        cnt++; lines e;
        for(e=S.top(),S.pop();;e=S.top(),S.pop()){
          if(v[e.x]!=cnt) v[e.x]=cnt, g[cnt].pb(e.x), g[e.x].pb(cnt);
          if(v[e.y]!=cnt) v[e.y]=cnt, g[cnt].pb(e.y), g[e.y].pb(cnt);
            
          if(e.x == x && e.y == to[i]) break;
        }
      }
    }
    else if(dfn[to[i]] < low[x]){
      S.push((lines){x,to[i]});
      low[x]=dfn[to[i]];
    }
}

void dfs(int x,int fa){
  if(x<=n){
      for(int i:g[x]) if(i!=fa)
        dfs(i,x), ans += siz[x] * (ll)siz[i], siz[x] += siz[i];
      ans+=siz[x] * (ll)(nn - siz[x] - 1);
      siz[x]++;
  }
  else{
      int sz=g[x].size()-2;
      for(int i:g[x]) if(i!=fa)
        dfs(i,x), ans += siz[x] * (ll)siz[i] * (ll)sz, siz[x] += siz[i];
      ans += siz[x] * (ll)(nn - siz[x]) * (ll)sz;
  }
}

inline void solve(){
  for(int i=1; i<=n; i++) if(!dfn[i]){
    nn=0,tarjan(i,0);
    dfs(i,0);
  }
}

int main(){
  scanf("%d %d", &n, &m); cnt=n;
  for(int i=1,uu,vv;i<=m;i++){
    scanf("%d %d", &uu, &vv);
    add(uu,vv), add(vv,uu);
  }
  solve(); 
  printf("%lld\n",ans<<1);
  return 0;
}

Compilation message (stderr)

count_triplets.cpp: In function 'void tarjan(int, int)':
count_triplets.cpp:19:34: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
   for(int i=hd[x]; i; i=ne[i]) if(to[i]!=fa)
                                  ^
count_triplets.cpp: In function 'int main()':
count_triplets.cpp:62:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &n, &m); cnt=n;
   ~~~~~^~~~~~~~~~~~~~~~~
count_triplets.cpp:64:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &uu, &vv);
     ~~~~~^~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 11 / 11
• Subtask 3: 0 / 8
• Subtask 4: 10 / 10
• Subtask 5: 0 / 13
• Subtask 6: 15 / 15
• Subtask 7: 0 / 20
• Subtask 8: 8 / 8
• Subtask 9: 0 / 10