697. Degree of an Array

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

class Solution {

public:
    int findShortestSubArray(vector<int>& nums) {
        unordered_map<int, int> map;
        unordered_map<int, int> map1;
        unordered_map<int, int> map2;
        vector<int> max_num;
        int max_freq = 1;
        for (int i = 0; i < nums.size(); i++) {
            if (map.count(nums[i]) == 0) {
                map[nums[i]] = 1;
                map1[nums[i]] = i;
            }
            else {
                map[nums[i]]++;
                max_freq = max(map[nums[i]], max_freq);
                map2[nums[i]] = i;
            }
        }
        unordered_map<int, int>::iterator iter;
        for (iter = map.begin(); iter != map.end(); iter++) {
            if (iter->second == max_freq) {
                max_num.push_back(iter->first);
            } 
        }
        if (max_num.size() == nums.size()) {
            return 1;
        }
        int close = INT_MAX;
        for (int i = 0; i < max_num.size(); i++) {
            close = min(map2[max_num[i]] - map1[max_num[i]] + 1, close);
        }
        return close;
    }

};

其实可以用一个map即可：

public int findShortestSubArray(int[] nums) {
        if (nums.length == 0 || nums == null) return 0;
        Map<Integer, int[]> map = new HashMap<>();
        for (int i = 0; i < nums.length; i++){
           if (!map.containsKey(nums[i])){
               map.put(nums[i], new int[]{1, i, i});  // the first element in array is degree, second is first index of this key, third is last index of this key
           } else {
               int[] temp = map.get(nums[i]);
               temp[0]++;
               temp[2] = i;
           }
        }
        int degree = Integer.MIN_VALUE, res = Integer.MAX_VALUE;
        for (int[] value : map.values()){
            if (value[0] > degree){
                degree = value[0];
                res = value[2] - value[1] + 1;
            } else if (value[0] == degree){
                res = Math.min( value[2] - value[1] + 1, res);
            } 
        }
        return res;
    }