Leetcode 1331

The idea of this solution is to:

Copy arr.
Then sort the copy
Then loop through the copy and add all the values and indexes of the copy to a map called m.
Then loop through 0 to len(arr) - 1, and make arr[i] = m[arr[i]].
Then return arr.

func arrayRankTransform(arr []int) []int {
	g := make([]int, len(arr))
	m := make(map[int]int)
	counter := 1

	copy(g, arr)
	sort.Ints(g)

	for i := range g {
		if i >= 1 && g[i] == g[i-1] {
			counter -= 1
		}
		m[g[i]] = counter
		counter++
	}

	for i := range arr {
		arr[i] = m[arr[i]]
	}

	return arr
}