Source address: https://leetcode.com/problems/maximum-gap/
Given an unsorted array, find the maximum difference between the successive elements in its sorted form.
Return 0 if the array contains less than 2 elements.
Input: [3,6,9,1] Output: 3 Explanation: The sorted form of the array is [1,3,6,9], either (3,6) or (6,9) has the maximum difference 3.
Input:  Output: 0 Explanation: The array contains less than 2 elements, therefore return 0.
This problem is easy. First, we sort, then loop the data, find the maximum difference.
Github address: https://github.com/tinyfool/leetcode/tree/master/src/p0164
To find other sort problems, see also Sort algorithms and problems.