# [LeetCode]#697. Degree of an Array

Environment: Python 3.7

Key technique: collections, Counter, enumerate, Dictionary

**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

**Analysis:**

Use Collections module Counter to calculate frequency of number in Input and use Dictionary to record number start and end location.

**Solution:**

`from collections import Counter`

class Solution:

def findShortestSubArray(self, nums) -> int:

num_dict = Counter( nums )

max_num = max( list( num_dict.values() ) )

start_end = dict()

for index, x in enumerate(nums):

if x not in start_end:

start_end[x] = [index, index]

else:

start_index = start_end[x][0]

start_end[x] = [ start_index, index]

degree = len( nums )

for num, occ in num_dict.items():

if occ == max_num:

end_index = start_end[num][1]

start_index = start_end[num][0]

degree = min( degree, end_index - start_index + 1)

return degree

**Submitted result:**

**Lesson learn:**

It is difficult to record start and end location, so I refer code in leetcode website. enumerate and dictionary is good function to this problem.

**Reference:**