go: add «912. Sort an Array»

Signed-off-by: Matej Focko <me@mfocko.xyz>

go/sort-an-array.go

@@ -0,0 +1,42 @@
+package main
+
+func sortArray(nums []int) []int {
+	swap := func(i, j int) {
+		nums[i], nums[j] = nums[j], nums[i]
+	}
+
+	partition := func(lower, upper int) (int, int) {
+		pivot := nums[(lower+upper)/2]
+
+		lt, eq, gt := lower, lower, upper
+
+		for eq <= gt {
+			if nums[eq] < pivot {
+				swap(eq, lt)
+				lt++
+				eq++
+			} else if nums[eq] > pivot {
+				swap(eq, gt)
+				gt--
+			} else {
+				eq++
+			}
+		}
+
+		return lt, gt
+	}
+
+	var quicksort func(int, int)
+	quicksort = func(lower, upper int) {
+		if lower >= upper || lower < 0 || upper < 0 {
+			return
+		}
+
+		lt, gt := partition(lower, upper)
+		quicksort(lower, lt-1)
+		quicksort(gt+1, upper)
+	}
+
+	quicksort(0, len(nums)-1)
+	return nums
+}