Count unique pairs in an array

unique_pairs.go

package main

import (
	"fmt"
)

type Pair struct {
	x int32
	y int32
}

// This is O(n^2 log n), expectation was O(n^2)
func countPairs(arr []int32, k int64) int32 {
	pairs := make(map[Pair]struct{})

	for i := 0; i < len(arr); i++ {
		for j := 0; j < len(arr); j++ {
			if i != j && int64(arr[i] + arr[j]) == k {
				x, y := arr[i], arr[j]
				if x > y {
					x, y = y, x // Sort pair to avoid duplicates
				}
				pairs[Pair{x,y}]= struct{}{}
			}
		}
	}

	return int32(len(pairs))
}

func main() {
	fmt.Println(countPairs([]int32{1,3,46,1,3,9}, 47), 1)
	fmt.Println(countPairs([]int32{6,6,3,9,3,5,1}, 12), 2)
}