Number of Good Pairs (LeetCode)

1512. Number of Good Pairs (Easy)

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

Hint:

Count how many times each number appears. If a number appears n times, then n * (n – 1) // 2 good pairs can be made with this number.

Number of Good Pairs (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;
    }
}

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