Codeforces 1006C.Three Parts of the Array(模拟)

#include <iostream>
#include <cstdio>
#include <cstring>
#define ll long long
using namespace std;
int n;
int pre[200005];

int main()
{
  cin>>n;
  for(int i=0;i<n;i++){
    cin>>pre[i];
  }
  ll l = 0, r = n - 1, sl = pre[0], sr = pre[n-1];
  ll ans = 0;
  while(l < r){
    if(sl == sr)
    ans = max(ans,sr);
    if(sl < sr){
      sl += pre[++l];
    }
    else{
      sr += pre[--r];
    }
  }
  cout<<ans<<endl;
  return 0;
}