12_sort

Author: leotyliu(刘天一)

go/12_sorts/MergeSort.go

@@ -1 +1,48 @@
 package _2_sorts
+
+func MergeSort(arr []int) {
+	arrLen := len(arr)
+	if arrLen <= 1 {
+		return
+	}
+
+	mergeSort(arr, 0, arrLen-1)
+}
+
+func mergeSort(arr []int, start, end int) {
+	if start >= end {
+		return
+	}
+
+	mid := (start + end) / 2
+	mergeSort(arr, start, mid)
+	mergeSort(arr, mid+1, end)
+	merge(arr, start, mid, end)
+}
+
+func merge(arr []int, start, mid, end int) {
+	tmpArr := make([]int, end-start+1)
+
+	i := start
+	j := mid + 1
+	k := 0
+	for ; i <= mid && j <= end; k++ {
+		if arr[i] < arr[j] {
+			tmpArr[k] = arr[i]
+			i++
+		} else {
+			tmpArr[k] = arr[j]
+			j++
+		}
+	}
+
+	for ; i <= mid; i++ {
+		tmpArr[k] = arr[i]
+		k++
+	}
+	for ; j <= end; j++ {
+		tmpArr[k] = arr[j]
+		k++
+	}
+	copy(arr[start:end+1], tmpArr)
+}

go/12_sorts/MergeSort_test.go

@@ -1 +1,13 @@
 package _2_sorts
+
+import "testing"
+
+func TestMergeSort(t *testing.T) {
+	arr := []int{5, 4}
+	MergeSort(arr)
+	t.Log(arr)
+
+	arr = []int{5, 4, 3, 2, 1}
+	MergeSort(arr)
+	t.Log(arr)
+}

go/12_sorts/QuickSort.go

@@ -1 +1,38 @@
 package _2_sorts
+
+func QuickSort(arr []int) {
+	arrLen := len(arr)
+	if arrLen <= 1 {
+		return
+	}
+	quickSort(arr, 0, arrLen-1)
+}
+
+func quickSort(arr []int, start, end int) {
+	if start >= end {
+		return
+	}
+
+	pivot := partition(arr, start, end)
+	quickSort(arr, start, pivot)
+	quickSort(arr, pivot+1, end)
+}
+
+func partition(arr []int, low, high int) int {
+	pivotV := arr[low]
+	for low < high {
+		for low < high && arr[high] > pivotV { //指针从右边开始向右找到一个比pivot小的数
+			high--
+		}
+		arr[low] = arr[high] //将这个数放到low位，注意第一次这个位置放的是pivot值，所以不会丢
+
+		for low < high && arr[low] < pivotV { //指针从左边开始向右找到第一个比pivot大的数
+			low++
+		}
+		arr[high] = arr[low] //将这个数赋值给之前的high指针，因为之前high指针指向的数已经被一定，所以不会丢
+	}
+
+	//最后将pivot的值放入合适位置，此时low与high相等
+	arr[low] = pivotV
+	return low
+}

go/12_sorts/QuickSort_test.go

@@ -1 +1,13 @@
 package _2_sorts
+
+import "testing"
+
+func TestQuickSort(t *testing.T) {
+	arr := []int{5, 4}
+	QuickSort(arr)
+	t.Log(arr)
+
+	arr = []int{5, 4, 3, 2, 1}
+	QuickSort(arr)
+	t.Log(arr)
+}