697. Degree of an Array

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Problem

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.

Code

class Solution {
    class Node {
        int count;
        int start;

        Node(int count, int start) {
            this.count = count;
            this.start = start;
        }
    }

    public int findShortestSubArray(int[] nums) {
        HashMap<Integer, Node> map = new HashMap<>();

        int res = 0;
        int degree = 0;

        for(int i = 0; i < nums.length; i++) {
            int num = nums[i];

            if(!map.containsKey(num)) {
                map.put(num, new Node(1, i));
            } else {
                Node node = map.get(num);
                node.count++;
                map.put(num, node);
            }

            Node node = map.get(num);
            if(node.count > degree) {
                degree = node.count;
                res = i - node.start + 1;
            } else if (node.count == degree) {
                res = Math.min(res, i - node.start + 1);
            }
        }

        return res;
    }
}