class Solution {
  public int numGoodPairs(int[] nums) {
    int pairCount = 0;
    Map<Integer, Integer> frequency = new HashMap<>();

    for (Integer num : nums) {
      frequency.put(num, frequency.getOrDefault(num, 0) + 1);
    }

    for (Map.Entry<Integer, Integer> entry : frequency.entrySet()) {
      int value = entry.getValue();
      pairCount += value * (value - 1) / 2;
    }
    return pairCount;
  }
}