Merge pull request wangzheng0822#81 from ScissorsFeet/master

12_sorts

Author: wangzheng0822

go/12_sorts/MergeSort.go

@@ -0,0 +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

@@ -0,0 +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

@@ -0,0 +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

@@ -0,0 +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)
+}

go/14_sorts/CountingSort.go

@@ -0,0 +1,33 @@
+package _4_sorts
+
+import "math"
+
+func CountingSort(a []int, n int) {
+if n <= 1 {
+return
+}
+
+var max int = math.MinInt32
+for i := range a {
+if a[i] > max {
+max = a[i]
+}
+}
+
+c := make([]int, max+1)
+for i := range a {
+c[a[i]]++
+}
+for i := 1; i <= max; i++ {
+c[i] += c[i-1]
+}
+
+r := make([]int, n)
+for i := range a {
+index := c[a[i]] - 1
+r[index] = a[i]
+c[a[i]]--
+}
+
+copy(a, r)
+}

go/14_sorts/CountingSort_test.go

@@ -0,0 +1,13 @@
+package _4_sorts
+
+import "testing"
+
+func TestCountingSort(t *testing.T) {
+arr := []int{5, 4}
+CountingSort(arr, len(arr))
+t.Log(arr)
+
+arr = []int{5, 4, 3, 2, 1}
+CountingSort(arr, len(arr))
+t.Log(arr)
+}