mirror of
https://github.com/krahets/hello-algo.git
synced 2024-12-26 00:46:28 +08:00
eb695937a4
* 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>
37 lines
1 KiB
Go
37 lines
1 KiB
Go
// 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
|
|
}
|