fuhouyin/hello-algo
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

feat: build_tree.c translation (#847)

Browse Source 
* feat: build_tree.c translation

* Update CMakeLists.txt

* chore: find with map

* change inordermap

* Update build_tree.c

---------

Co-authored-by: Yudong Jin <krahets@163.com>
This commit is contained in:
lucas 2023-10-17 21:47:16 +08:00 committed by GitHub
parent ea7275ab6a
commit 37872726b0
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 61 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
codes/c/chapter_divide_and_conquer/CMakeLists.txt
View File

@ -1,2 +1,3 @@
add_executable(binary_search_recur binary_search_recur.c)
add_executable(hanota hanota.c)
add_executable(build_tree build_tree.c)

60
codes/c/chapter_divide_and_conquer/build_tree.c Normal file
View File

@ -0,0 +1,60 @@
/**
* File : build_tree.c
* Created Time: 2023-10-16
* Author : lucas (superrat6@gmail.com)
*/
#include "../utils/common.h"
// 假设所有元素都小于 1000
#define MAX_N 1000
/* 构建二叉树：分治 */
TreeNode* dfs(int* preorder, int* inorderMap, int i, int l, int r, int size) {
// 子树区间为空时终止
if (r - l < 0)
return NULL;
// 初始化根节点
TreeNode* root = (TreeNode*)malloc(sizeof(TreeNode));
root->val = preorder[i];
root->left = NULL;
root->right = NULL;
// 查询 m ，从而划分左右子树
int m = inorderMap[preorder[i]];
// 子问题：构建左子树
root->left = dfs(preorder, inorderMap, i + 1, l, m - 1, size);
// 子问题：构建右子树
root->right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r, size);
// 返回根节点
return root;
}
/* 构建二叉树 */
TreeNode* buildTree(int* preorder, int preorderSize, int* inorder, int inorderSize) {
// 初始化哈希表，存储 inorder 元素到索引的映射
int* inorderMap = (int*)malloc(sizeof(int) * MAX_N);
for (int i = 0; i < inorderSize; i++) {
inorderMap[inorder[i]] = i;
}
TreeNode* root = dfs(preorder, inorderMap, 0, 0, inorderSize - 1, inorderSize);
free(inorderMap);
return root;
}
/* Driver Code */
int main() {
int preorder[] = {3, 9, 2, 1, 7};
int inorder[] = {9, 3, 1, 2, 7};
int preorderSize = sizeof(preorder) / sizeof(preorder[0]);
int inorderSize = sizeof(inorder) / sizeof(inorder[0]);
printf("前序遍历 = ");
printArray(preorder, preorderSize);
printf("中序遍历 = ");
printArray(inorder, inorderSize);
TreeNode* root = buildTree(preorder, preorderSize, inorder, inorderSize);
printf("构建的二叉树为：\n");
printTree(root);
return 0;
}