2018百度之星初赛（B）1004

最大化最小值，二分答案

#include<cstdio>
#include<algorithm>
#include<iostream>
#include<cmath>
#define ll long long
using namespace std;
const int N = 3e5+9;
const int inf = 0x3f3f3f3f;
int a[N];
int n;
int work(int mid)
{
    ll o1=0,o2=0;
    for(int i = 0; i<n; i++){
        if(a[i]<mid) o1 += mid-a[i];
        else if(a[i]>mid) o2 += (a[i]-mid)/2;
    }
    if(o1<=o2) return 1;
    else return 0;
}
int main()
{
   // freopen("in.txt","r",stdin);
    ios::sync_with_stdio(false);
    int t; cin>>t;
    while(t--){
        cin>>n;
        int minn=inf,maxx = -inf;
        for(int i = 0; i<n; i++) {
            cin>>a[i];
            minn=min(minn,a[i]);
            maxx = max(maxx,a[i]);
        }
        int l = 0,r = maxx;
        while(l<r){
             int mid = (l+r+1)>>1;
             if(work(mid)) l=mid;
             else r = mid-1;
        }
       cout<<l<<endl; 
    }
    return 0;
}