More efficient bubble sort (#141)

Author: spring1843

array/bubble_sort.go

@@ -2,10 +2,13 @@ package array
 
 // BubbleSort solves the problem in O(n^2) time and O(1) space.
 func BubbleSort(input []int) {
-	for i := range input {
-		for j := range input {
-			if input[i] < input[j] {
-				input[i], input[j] = input[j], input[i]
+	swapped := true
+	for swapped {
+		swapped = false
+		for i := 1; i < len(input); i++ {
+			if input[i] < input[i-1] {
+				input[i], input[i-1] = input[i-1], input[i]
+				swapped = true
 			}
 		}
 	}