City Upgrades

Time limit: 

1000 ms

Memory limit: 

128 MB

There are N cities placed in a line. For each city ii you know its coodinate x​​. You can upgrade exactly K of these cities. Your goal is to choose what cities to upgrade in a way the minimizes the maximum distance between a regular city and the closest upgraded one.

Standard input

The first line contains two integers N and K.

The second line contains N integers representing the coordinates of the cities.

Standard output

Print a single integer representing the smallest maximum distance between a regular city and the closest upgraded one.

Constraints and notes

• 1<= K < N<=10^5​​ 
• 0≤x​i​​≤10​^9

Simple Input:

5 21 2 4 5 10

Simple Ouput:

3

题意：在数轴上有n个点，给定一个k，让你选出k个点，使得剩下n-k个点与这k个点之间的最短距离最小。

解法：二分枚举，然后检查即可