1512. Number of Good Pairs

Problem

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

Solution (Java)

class Solution {
    public int numIdenticalPairs(int[] nums) {
        int count = 0;
        for (int i = 0; i < nums.length; i++) {
            for (int j = i + 1; j < nums.length; j++) {
                if (nums[i] == nums[j]) {
                    count++;
                }
            }
        }
        return count;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).