Aggressive cows（二分）

Aggressive cows

Farmer John has built a new long barn, with N (2 <= N <= 100,000) stalls. The stalls are located along a straight line at positions x1,…,xN (0 <= xi <= 1,000,000,000).

His C (2 <= C <= N) cows don’t like this barn layout and become aggressive towards each other once put into a stall. To prevent the cows from hurting each other, FJ want to assign the cows to the stalls, such that the minimum distance between any two of them is as large as possible. What is the largest minimum distance?
Input

• Line 1: Two space-separated integers: N and C

• Lines 2…N+1: Line i+1 contains an integer stall location, xi
  Output

• Line 1: One integer: the largest minimum distance
  Sample Input
  5 3
  1
  2
  8
  4
  9
  Sample Output
  3
  Hint
  OUTPUT DETAILS:

FJ can put his 3 cows in the stalls at positions 1, 4 and 8, resulting in a minimum distance of 3.

Huge input data,scanf is recommended.

最后一句。。。一直没看到，cin/cout可能会超时
需要换成scanf/printf
如下列代码加一行ios。。。(挂掉同步流)也行
ac代码：

#include<iostream>
#include<algorithm>
using namespace std;
int n,c;
long long stall[100007];
bool check(int mid){
	int ans=1;
	int temp=stall[0];
	for(int i=1;i<n;i++){
		if(stall[i]-temp>=mid){
			ans++;
			temp=stall[i];
			if(ans>=c) return true;
		}
	}
	
	
	return false;
}
int main(){
	ios::sync_with_stdio(0);
	cin.tie(),cout.tie();
	cin>>n>>c;
	for(int i=0;i<n;i++) cin>>stall[i];
	sort(stall,stall+n);
	int l=0,r=stall[n-1]-stall[0],mid;
	while(r>=l){
		mid=(l+r)/2;
		if(check(mid)){
			l=mid+1;
		}
		else r=mid-1;
	}
	cout<<l-1<<endl;
	return 0;
}