[二分答案]p1m2

#include <iostream>
#include<cstdio>
#include<algorithm>
typedef long long ll;
using namespace std;

ll n,a[300010];

bool ok(ll x){
  ll sub=0,add=0;
  for(ll i=1;i<=n;i++) {
    if(a[i]<x) add+=(x-a[i]);
    else if((a[i]-x)%2==0) sub+=(a[i]-x)/2;
    else sub+=(a[i]-x-1)/2;
  }
  return sub>=add;
}

int main()
{
    ll t;scanf("%lld",&t);
    while(t--){
        scanf("%lld",&n);
        for(ll i=1;i<=n;i++) scanf("%lld",&a[i]);
        sort(a+1,a+1+n);
        ll l=a[1],r=a[n];
        while(l<=r){
            ll mid=(l+r)/2;
            if(ok(mid)) l=mid+1;
            else r=mid-1;
        }
        printf("%lld\n",r);
    }
    return 0;
}