1512. Number of Good Pairs
Array
Hash Table
Math
Counting
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.
Examples
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 <= 1001 <= nums[i] <= 100