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697. Degree of an Array

  • Time: $O(n)$
  • Space: $O(n)$
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class Solution {
 public:
  int findShortestSubArray(vector<int>& nums) {
    int ans = 0;
    int degree = 0;
    unordered_map<int, int> debut;
    unordered_map<int, int> count;

    for (int i = 0; i < nums.size(); ++i) {
      const int num = nums[i];
      if (!debut.count(num))
        debut[num] = i;
      if (++count[num] > degree) {
        degree = count[num];
        ans = i - debut[num] + 1;
      } else if (count[num] == degree) {
        ans = min(ans, i - debut[num] + 1);
      }
    }

    return ans;
  }
};

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class Solution {
  public int findShortestSubArray(int[] nums) {
    int ans = 0;
    int degree = 0;
    Map<Integer, Integer> debut = new HashMap<>();
    Map<Integer, Integer> count = new HashMap<>();

    for (int i = 0; i < nums.length; ++i) {
      final int num = nums[i];
      debut.putIfAbsent(num, i);
      count.merge(num, 1, Integer::sum);
      if (count.get(num) > degree) {
        degree = count.get(num);
        ans = i - debut.get(num) + 1;
      } else if (count.get(num) == degree) {
        ans = Math.min(ans, i - debut.get(num) + 1);
      }
    }

    return ans;
  }
}

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class Solution:
  def findShortestSubArray(self, nums: List[int]) -> int:
    ans = 0
    degree = 0
    debut = {}
    count = collections.Counter()

    for i, num in enumerate(nums):
      debut.setdefault(num, i)
      count[num] += 1
      if count[num] > degree:
        degree = count[num]
        ans = i - debut[num] + 1
      elif count[num] == degree:
        ans = min(ans, i - debut[num] + 1)

    return ans