Leetcode - 1512. Number of Good Pairs

Leetcode - 1512. Number of Good Pairs

• 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.

Solution 1

func numIdenticalPairs(nums []int) int {
    pairCount := 0
	first, second := 0, 1

	for first=0; first<len(nums)-1; first++{
		for second=1; second<len(nums); second++{
			if nums[first]==nums[second] && first<second{
				pairCount++
			}
		}
	}
	return pairCount
}

Solution 2 (Optimized)

func numIdenticalPairs(nums []int) int {
    pairCount := 0
	mapCount := make(map[int]int)

    for _, num := range nums{
        mapCount[num]++

        // every new occurrence of a number can be paired with every previous occurrence
		    // so if a number has already appeared 'p' times, we will have 'p-1' new pairs
        pairCount = pairCount+(mapCount[num]-1)
    }
	return pairCount
}