Leetcode 697. Degree of an Array 最大频率数字的最短子数组 Python实现

题目：

Given a non-empty array of non-negative integers nums, the degree of this array is defined as the maximum frequency of any one of its elements.

Your task is to find the smallest possible length of a (contiguous) subarray of nums, that has the same degree as nums.

Example 1:

Input: [1, 2, 2, 3, 1]
Output: 2
Explanation: 
The input array has a degree of 2 because both elements 1 and 2 appear twice.
Of the subarrays that have the same degree:
[1, 2, 2, 3, 1], [1, 2, 2, 3], [2, 2, 3, 1], [1, 2, 2], [2, 2, 3], [2, 2]
The shortest length is 2. So return 2.

Example 2:

Input: [1,2,2,3,1,4,2]
Output: 6

题目有点搞，大概意思是说，首先找到出现频率最高的数字，这个频率就是degree。然后再在原始数组里找一个子数组，子数组必须是连续的，使得这个子数组的degree与原始数组是一样的，请问这个子数组最短是多少。