F - Triangles

Posted 2020-12-29 shengge-777

#include <iostream>
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
#include<queue>
#include<map>
using namespace std;
map<int,int>vis;
int main()
{
int n,m,a[100001]={0},j,temp=0,i,k,pre[100001]={0};
cin>>n;
int sum=0;
for(i=1;i<=n;i++)
{
    cin>>a[i];
    pre[i]=a[i]+pre[i-1];
    vis[pre[i]]++;
    sum+=a[i];
}
if(sum%3!=0)
    cout<<0<<endl;
else
{
    int ans=sum/3;
    int count=0,temp=0,cnt=0;
 for(i=1;i<=n;i++)
 {
         if(vis[ans+pre[i]]&&vis[ans*2+pre[i]]) cnt++;
}
 cout<<cnt<<endl;
}

return 0;
}