2018百度之星初赛

HDU6383 p1m2

二分

#include<bits/stdc++.h>
using namespace std;
const int MAX=3e5+5;
const int INF=0x3f3f3f3f;
int t,n,a[MAX];
bool check(long long x)
{
    long long cnt1=0,cnt2=0;
    int sub;
    for(int i=0;i<n;++i)
    {
        sub=a[i]-x;
        if(sub>0) cnt1+=sub/2;
        else cnt2+=-sub;
    }
    return cnt1>=cnt2;
}
int main()
{
    int min_,max_;
    scanf("%d",&t);
    while(t--)
    {
        min_=INF;max_=-INF;
        scanf("%d",&n);
        for(int i=0;i<n;++i)
        {
            scanf("%d",&a[i]);
            min_=min(a[i],min_);
            max_=max(a[i],max_);
        }
        int l=min_,r=max_,mid,ans=-1;
        while(l<=r)
        {
            mid=(l+r)>>1;
            if(check(mid)) l=mid+1,ans=mid;
            else r=mid-1;
        }
        printf("%d\n",ans);
    }
    return 0;
}