Submission #4019396

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

//repetition
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i, n) for(int i = 0; i < (int)(n); i++)

//container util
#define all(x) (x).begin(),(x).end()

//typedef
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VLL;
typedef vector<VLL> VVLL;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;


//conversion
inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}


int main(){
  int n;
  cin >> n;

  VLL A(n);
  map<ll,ll> num_cnt;
  rep(i,n){
    cin >> A[i];
    num_cnt[i+1] = A[i];
  }

  sort(all(A));
  ll ans = 0;
  FOR(i,1,n+1){
    ll tmp = min(num_cnt[A[i]-1],num_cnt[A[i]]);
    //cout << "tmp " << tmp << endl;
    ans += tmp;
    num_cnt[A[i]]    -= tmp;
    num_cnt[A[i]-1]  -= tmp;
    ans += num_cnt[i-1]/2;
  }
  ans += num_cnt[n-1]/2;
  cout << ans << endl;
  return 0;
}

Submission Info

Judge Result