C++11(clang++ 3.9) 解法, 执行用时: 30ms, 内存消耗: 1672K, 提交时间: 2019-12-19 12:35:51

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> P;

ll a[200005];
int main()
{
    ll n,k;
    scanf("%lld%lld",&n,&k);
    ll A=0;
    for(int i=1;i<=n;i++)scanf("%lld",&a[i]),A+=a[i];
    sort(a+1,a+n+1,greater<ll>());
    ll X=0;
    for(ll w=1;w<k;w++)
    {
        X+=a[w];
        A-=a[w];
        if(X*(k-w)>w*A)X=A*w/(k-w);
    }
    ll sum=X+A;
    printf("%lld\n",sum/k);
	return 0;
}

C++14(g++5.4) 解法, 执行用时: 35ms, 内存消耗: 2016K, 提交时间: 2020-02-24 11:31:21

#include<stdio.h>
#include<algorithm>
using namespace std;
#define ll long long
int main()
{
	ll n,m,a[100010],b[100010]={0};
	scanf("%lld%lld",&n,&m);
	for(int i=1;i<=n;i++)scanf("%lld",&a[i]);
	sort(a+1,a+n+1);
	for(int i=1;i<=n;i++)b[i]=b[i-1]+a[i];
	ll t=m;
	ll ans;
	for(int i=n;i>n-m;i--){
		if(b[i]/t>=a[i]){
			ans=b[i]/t;
			break;
		}
		else t--;
		if(i==n-m+1)ans=a[i];		
	}
	printf("%lld\n",ans);
}