Number of Good Pairs

You are given an array of integers nums, return the number of good pairs.

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

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