public class DayCode {    public static void main(String[] args) {        int[] nums = new int[]{1,2,2,3,1,4,2};        int ans = new DayCode().findShortestSubArray(nums);        System.out.println("ans is " + ans);    }
    /**     * https://leetcode-cn.com/problems/degree-of-an-array/     * 时间复杂度是O(n),空间复杂度是O(n)     * @param nums     * @return     */    public int findShortestSubArray(int[] nums) {        int ans = Integer.MAX_VALUE;        Map<Integer, DegreeNode> numDegreeMap = new HashMap<>();        int maxDegree = 0;        for (int i = 0 ; i < nums.length; i++) {            DegreeNode node = new DegreeNode();            if (numDegreeMap.containsKey(nums[i])) {                node = numDegreeMap.get(nums[i]);                node.degree += 1;            } else {                node.degree = 1;                node.beginIdx = i;            }            node.endIdx = i;            maxDegree = Math.max(maxDegree, node.degree);            numDegreeMap.put(nums[i], node);        }
        for (DegreeNode item : numDegreeMap.values()) {            if (item.degree == maxDegree) {                ans = Math.min(ans, item.endIdx - item.beginIdx + 1);            }        }        return ans;    }
    class DegreeNode {        int degree;        int beginIdx;        int endIdx;
        public DegreeNode () {            this.degree = 0;            this.beginIdx = 0;            this.endIdx = 0;        }    }}