我是题解

#include<bits/stdc++.h>
using namespace std;
#define int unsigned long long
int a[11451454],n,k,l,r;
bool check(int o){
	int t=1,f=0;
	f=a[1];
	for(int i=2;i<=n;i++){
		if(a[i]-f>o){
			t++;
			f=a[i];
			//cout<<f<<" ";
			if(t==k){
				//cout<<endl;
				return 0;
			}
		}
	}
	//cout<<endl;
	return 1;
}
signed main(){
    cin>>n>>k;
    for(int i=1;i<=n;i++){
    	cin>>a[i];
    	r+=a[i];
	}
    l=0;r*=2;
    sort(a+1,a+n+1);
    while(r-l>1){
    	int m=(r+l)/2;
    	//cout<<r<<"   "<<l<<endl<<endl;
    	if(check(m))r=m;
		else l=m;
	}
	//cout<<r<<"   "<<l<<endl<<endl;
	cout<<r;
}