Add divide and conquer go code (#638)

* feat: Add Go code to binary search recursion under divide and conquer

* style: Code comment standardization

* style: modify function comment

* fix: fixed error when the list is empty

* Update print_utils.go

* Delete print_utils_test.go

* feat: add Go code to divide and conquer

* Update build_tree.go

* style: modify function name

---------

Co-authored-by: Yudong Jin <krahets@163.com>

codes/go/chapter_divide_and_conquer/build_tree.go

@@ -0,0 +1,37 @@
+// File: build_tree.go
+// Created Time: 2023-07-20
+// Author: hongyun-robot (1836017030@qq.com)
+
+package chapter_divide_and_conquer
+
+import . "github.com/krahets/hello-algo/pkg"
+
+/* 构建二叉树：分治 */
+func dfsBuildTree(preorder, inorder []int, hmap map[int]int, i, l, r int) *TreeNode {
+	// 子树区间为空时终止
+	if r-l < 0 {
+		return nil
+	}
+	// 初始化根节点
+	root := NewTreeNode(preorder[i])
+	// 查询 m ，从而划分左右子树
+	m := hmap[preorder[i]]
+	// 子问题：构建左子树
+	root.Left = dfsBuildTree(preorder, inorder, hmap, i+1, l, m-1)
+	// 子问题：构建右子树
+	root.Right = dfsBuildTree(preorder, inorder, hmap, i+1+m-l, m+1, r)
+	// 返回根节点
+	return root
+}
+
+/* 构建二叉树 */
+func buildTree(preorder, inorder []int) *TreeNode {
+	// 初始化哈希表，存储 inorder 元素到索引的映射
+	hmap := make(map[int]int, len(inorder))
+	for i := 0; i < len(inorder); i++ {
+		hmap[inorder[i]] = i
+	}
+
+	root := dfsBuildTree(preorder, inorder, hmap, 0, 0, len(inorder)-1)
+	return root
+}

codes/go/chapter_divide_and_conquer/build_tree_test.go

@@ -0,0 +1,24 @@
+// File: build_tree_test.go
+// Created Time: 2023-07-20
+// Author: hongyun-robot (1836017030@qq.com)
+
+package chapter_divide_and_conquer
+
+import (
+	"fmt"
+	. "github.com/krahets/hello-algo/pkg"
+	"testing"
+)
+
+func TestBuildTree(t *testing.T) {
+	preorder := []int{3, 9, 2, 1, 7}
+	inorder := []int{9, 3, 1, 2, 7}
+	fmt.Print("前序遍历 = ")
+	PrintSlice(preorder)
+	fmt.Print("中序遍历 = ")
+	PrintSlice(inorder)
+
+	root := buildTree(preorder, inorder)
+	fmt.Println("构建的二叉树为：")
+	PrintTree(root)
+}

codes/go/chapter_divide_and_conquer/hanota.go

@@ -0,0 +1,39 @@
+// File: hanota.go
+// Created Time: 2023-07-21
+// Author: hongyun-robot (1836017030@qq.com)
+
+package chapter_divide_and_conquer
+
+import "container/list"
+
+/* 移动一个圆盘 */
+func move(src, tar *list.List) {
+	// 从 src 顶部拿出一个圆盘
+	pan := src.Back()
+	// 将圆盘放入 tar 顶部
+	tar.PushBack(pan.Value)
+	// 移除 src 顶部圆盘
+	src.Remove(pan)
+}
+
+/* 求解汉诺塔：问题 f(i) */
+func dfsHanota(i int, src, buf, tar *list.List) {
+	// 若 src 只剩下一个圆盘，则直接将其移到 tar
+	if i == 1 {
+		move(src, tar)
+		return
+	}
+	// 子问题 f(i-1) ：将 src 顶部 i-1 个圆盘借助 tar 移到 buf
+	dfsHanota(i-1, src, tar, buf)
+	// 子问题 f(1) ：将 src 剩余一个圆盘移到 tar
+	move(src, tar)
+	// 子问题 f(i-1) ：将 buf 顶部 i-1 个圆盘借助 src 移到 tar
+	dfsHanota(i-1, buf, src, tar)
+}
+
+/* 求解汉诺塔 */
+func hanota(A, B, C *list.List) {
+	n := A.Len()
+	// 将 A 顶部 n 个圆盘借助 B 移到 C
+	dfsHanota(n, A, B, C)
+}

codes/go/chapter_divide_and_conquer/hanota_test.go

@@ -0,0 +1,39 @@
+// File: hanota_test.go
+// Created Time: 2023-07-21
+// Author: hongyun-robot (1836017030@qq.com)
+
+package chapter_divide_and_conquer
+
+import (
+	"container/list"
+	"fmt"
+	. "github.com/krahets/hello-algo/pkg"
+	"testing"
+)
+
+func TestHanota(t *testing.T) {
+	// 列表尾部是柱子顶部
+	A := list.New()
+	for i := 5; i > 0; i-- {
+		A.PushBack(i)
+	}
+	B := list.New()
+	C := list.New()
+	fmt.Println("初始状态下：")
+	fmt.Print("A = ")
+	PrintList(A)
+	fmt.Print("B = ")
+	PrintList(B)
+	fmt.Print("C = ")
+	PrintList(C)
+
+	hanota(A, B, C)
+
+	fmt.Println("圆盘移动完成后：")
+	fmt.Print("A = ")
+	PrintList(A)
+	fmt.Print("B = ")
+	PrintList(B)
+	fmt.Print("C = ")
+	PrintList(C)
+}