Aggressive cows

Time Limit: 1000MS	Memory Limit: 65536K
Total Submissions: 14220	Accepted: 6887

Description

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.

Source

Point:

1.區間為[lb,ub)前閉後開

#include<iostream>  
#include<cstdio>  
#include<cstring>  
#include<string>  
#include<cmath>  
#include<queue>  
#include<stack>  
#include<vector>  
#include<map>  
#include<algorithm>  
using namespace std;  
#define ll long long  
#define ms(a,b)  memset(a,b,sizeof(a))  
const int M=1e5+10;  
const int inf=0x3f3f3f3f;  
const int mod=1e9+7;  
int a[M]; 
int i,j,k,n,m;

bool check(int mid)
{
	int last=0;
	for(int i=1;i<k;i++){
		int cur=last+1;
		while(cur<n&&(a[cur]-a[last])<mid)cur++;
		if(cur==n)return false;
		last=cur;
	}
	return true;
}


int main()
{
	while(~scanf("%d%d",&n,&k)){
		for(int i=0;i<n;i++)
			scanf("%d",&a[i]);
		sort(a,a+n);
		int lb=0,ub=1000000000;
		while(ub-lb>1){
			int mid=(lb+ub)/2;
			if(check(mid))lb=mid;
			else ub=mid;
		}
		printf("%d\n",lb);
	}
	return 0;
}