README_EN.md

697. Degree of an Array

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Description

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: nums = [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: nums = [1,2,2,3,1,4,2]
Output: 6
Explanation: 
The degree is 3 because the element 2 is repeated 3 times.
So [2,2,3,1,4,2] is the shortest subarray, therefore returning 6.

 

Constraints:

• nums.length will be between 1 and 50,000.
• nums[i] will be an integer between 0 and 49,999.

Solutions

Python3

class Solution:
    def findShortestSubArray(self, nums: List[int]) -> int:
        mapper = {}
        for i, v in enumerate(nums):
            if v in mapper:
                arr = mapper[v]
                arr[0] += 1
                arr[2] = i
            else:
                arr = [1, i, i]
                mapper[v] = arr
        max_degree = min_len = 0
        for arr in mapper.values():
            if max_degree < arr[0]:
                max_degree = arr[0]
                min_len = arr[2] - arr[1] + 1
            elif max_degree == arr[0]:
                min_len = min(min_len, arr[2] - arr[1] + 1)
        return min_len

Java

class Solution {
    public int findShortestSubArray(int[] nums) {
        Map<Integer, int[]> mapper = new HashMap<>();
        for (int i = 0, n = nums.length; i < n; ++i) {
            if (mapper.containsKey(nums[i])) {
                int[] arr = mapper.get(nums[i]);
                ++arr[0];
                arr[2] = i;
            } else {
                int[] arr = new int[]{1, i, i};
                mapper.put(nums[i], arr);
            }
        }

        int maxDegree = 0, minLen = 0;
        for (Map.Entry<Integer, int[]> entry : mapper.entrySet()) {
            int[] arr = entry.getValue();
            if (maxDegree < arr[0]) {
                maxDegree = arr[0];
                minLen = arr[2] - arr[1] + 1;
            } else if (maxDegree == arr[0]) {
                minLen = Math.min(minLen, arr[2] - arr[1] + 1);
            }
        }
        return minLen;
    }
}

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