LeetCode - Number of Good Pairs

Given an array of integers nums.

A pair (i,j) is called good if nums[i] == nums[j] and i < j.

Return the number of good pairs.

 

Example 1:

Input: nums = [1,2,3,1,1,3]
Output: 4
Explanation: There are 4 good pairs (0,3), (0,4), (3,4), (2,5) 0-indexed.
Example 2:

Input: nums = [1,1,1,1]
Output: 6
Explanation: Each pair in the array are good.
Example 3:

Input: nums = [1,2,3]
Output: 0
 

Constraints:

1 <= nums.length <= 100
1 <= nums[i] <= 100

class Solution {
    public int numIdenticalPairs(int[] nums) {
        Map<Integer, Integer> map = new HashMap<>();
        int count = 0;
        for (int i = 0; i< nums.length; i++) {
            if (map.containsKey(nums[i])) {
                count = count + map.get(nums[i]);
                map.put(nums[i], map.get(nums[i])+1);
            }
            else {
                map.put(nums[i], 1);
            }
        }
        return count;
    }
}