Skip to content

Commit ef96e9c

Browse files
yanglbmeyanglbme
committed
feat: update leetcode solutions: No.0235, No.0236
1 parent 977b537 commit ef96e9c

File tree

12 files changed

+251
-40
lines changed

12 files changed

+251
-40
lines changed

Diff for: ‎README.md

+2-2
Original file line numberDiff line numberDiff line change
@@ -49,8 +49,8 @@
4949

5050
### 二叉树
5151

52-
1. [二叉树的最近公共祖先](./lcof/面试题68%20-%20II.%20二叉树的最近公共祖先/README.md)
53-
1. [二叉搜索树的最近公共祖先](./lcof/面试题68%20-%20I.%20二叉搜索树的最近公共祖先/README.md)
52+
1. [二叉树的最近公共祖先](./solution/0200-0299/0235.Lowest%20Common%20Ancestor%20of%20a%20Binary%20Search%20Tree/README.md)
53+
1. [二叉搜索树的最近公共祖先](./solution/0200-0299/0236.Lowest%20Common%20Ancestor%20of%20a%20Binary%20Tree/README.md)
5454

5555
### 数学
5656

Diff for: ‎README_EN.md

+4
Original file line numberDiff line numberDiff line change
@@ -47,6 +47,10 @@ Complete solutions to [LeetCode](https://leetcode-cn.com/problemset/all/), [LCOF
4747

4848
### Binary Tree
4949

50+
1. [Lowest Common Ancestor of a Binary Tree](./solution/0200-0299/0236.Lowest%20Common%20Ancestor%20of%20a%20Binary%20Tree/README_EN.md)
51+
1. [Lowest Common Ancestor of a Binary Search Tree](./solution/0200-0299/0235.Lowest%20Common%20Ancestor%20of%20a%20Binary%20Search%20Tree/README_EN.md)
52+
53+
5054
### Math
5155

5256
1. [Set Mismatch](./solution/0600-0699/0645.Set%20Mismatch/README_EN.md)

Diff for: ‎solution/0200-0299/0235.Lowest Common Ancestor of a Binary Search Tree/README.md

+47-5
Original file line numberDiff line numberDiff line change
@@ -10,9 +10,7 @@
1010

1111
<p>例如，给定如下二叉搜索树:&nbsp; root =&nbsp;[6,2,8,0,4,7,9,null,null,3,5]</p>
1212

13-
<p><img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2018/12/14/binarysearchtree_improved.png" style="height: 190px; width: 200px;"></p>
14-
15-
<p>&nbsp;</p>
13+
![](./images/binarysearchtree_improved.png)
1614

1715
<p><strong>示例 1:</strong></p>
1816

@@ -41,21 +39,65 @@
4139
## 解法
4240
<!-- 这里可写通用的实现逻辑 -->
4341

42+
从上到下搜索，找到第一个值位于 `[p, q]` 之间的结点即可。既可以用迭代实现，也可以用递归实现。
4443

4544
<!-- tabs:start -->
4645

4746
### **Python3**
4847
<!-- 这里可写当前语言的特殊实现逻辑 -->
4948

5049
```python
51-
50+
# Definition for a binary tree node.
51+
# class TreeNode:
52+
# def __init__(self, x):
53+
# self.val = x
54+
# self.left = None
55+
# self.right = None
56+
57+
class Solution:
58+
def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
59+
if p == q:
60+
return p
61+
while root:
62+
if root.val < p.val and root.val < q.val:
63+
root = root.right
64+
elif root.val > p.val and root.val > q.val:
65+
root = root.left
66+
else:
67+
return root
5268
```
5369

5470
### **Java**
5571
<!-- 这里可写当前语言的特殊实现逻辑 -->
5672

5773
```java
58-
74+
/**
75+
* Definition for a binary tree node.
76+
* public class TreeNode {
77+
* int val;
78+
* TreeNode left;
79+
* TreeNode right;
80+
* TreeNode(int x) { val = x; }
81+
* }
82+
*/
83+
84+
class Solution {
85+
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
86+
if (p == q) {
87+
return p;
88+
}
89+
while (root != null) {
90+
if (root.val < p.val && root.val < q.val) {
91+
root = root.right;
92+
} else if (root.val > p.val && root.val > q.val) {
93+
root = root.left;
94+
} else {
95+
return root;
96+
}
97+
}
98+
return null;
99+
}
100+
}
59101
```
60102

61103
### **...**

Diff for: ‎solution/0200-0299/0235.Lowest Common Ancestor of a Binary Search Tree/README_EN.md

+46-10
Original file line numberDiff line numberDiff line change
@@ -13,11 +13,7 @@
1313

1414
<p>Given binary search tree:&nbsp; root =&nbsp;[6,2,8,0,4,7,9,null,null,3,5]</p>
1515

16-
<img alt="" src="https://assets.leetcode.com/uploads/2018/12/14/binarysearchtree_improved.png" style="width: 200px; height: 190px;" />
17-
18-
<p>&nbsp;</p>
19-
20-
16+
![](./images/binarysearchtree_improved.png)
2117

2218
<p><strong>Example 1:</strong></p>
2319

@@ -60,11 +56,8 @@
6056

6157

6258
<ul>
63-
6459
<li>All of the nodes&#39; values will be unique.</li>
65-
6660
<li>p and q are different and both values will&nbsp;exist in the BST.</li>
67-
6861
</ul>
6962

7063

@@ -78,13 +71,56 @@
7871
### **Python3**
7972

8073
```python
81-
74+
# Definition for a binary tree node.
75+
# class TreeNode:
76+
# def __init__(self, x):
77+
# self.val = x
78+
# self.left = None
79+
# self.right = None
80+
81+
class Solution:
82+
def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
83+
if p == q:
84+
return p
85+
while root:
86+
if root.val < p.val and root.val < q.val:
87+
root = root.right
88+
elif root.val > p.val and root.val > q.val:
89+
root = root.left
90+
else:
91+
return root
8292
```
8393

8494
### **Java**
8595

8696
```java
87-
97+
/**
98+
* Definition for a binary tree node.
99+
* public class TreeNode {
100+
* int val;
101+
* TreeNode left;
102+
* TreeNode right;
103+
* TreeNode(int x) { val = x; }
104+
* }
105+
*/
106+
107+
class Solution {
108+
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
109+
if (p == q) {
110+
return p;
111+
}
112+
while (root != null) {
113+
if (root.val < p.val && root.val < q.val) {
114+
root = root.right;
115+
} else if (root.val > p.val && root.val > q.val) {
116+
root = root.left;
117+
} else {
118+
return root;
119+
}
120+
}
121+
return null;
122+
}
123+
}
88124
```
89125

90126
### **...**

Diff for: ‎solution/0200-0299/0235.Lowest Common Ancestor of a Binary Search Tree/Solution.java

+21-8
Original file line numberDiff line numberDiff line change
@@ -1,14 +1,27 @@
1+
/**
2+
* Definition for a binary tree node.
3+
* public class TreeNode {
4+
* int val;
5+
* TreeNode left;
6+
* TreeNode right;
7+
* TreeNode(int x) { val = x; }
8+
* }
9+
*/
10+
111
class Solution {
212
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
3-
if (root == null || root == p || root == q) {
4-
return root;
13+
if (p == q) {
14+
return p;
515
}
6-
TreeNode leftNode = lowestCommonAncestor(root.left, p, q);
7-
TreeNode rightNode = lowestCommonAncestor(root.right, p, q);
8-
if (leftNode != null && rightNode != null) {
9-
return root;
16+
while (root != null) {
17+
if (root.val < p.val && root.val < q.val) {
18+
root = root.right;
19+
} else if (root.val > p.val && root.val > q.val) {
20+
root = root.left;
21+
} else {
22+
return root;
23+
}
1024
}
11-
return leftNode != null ? leftNode : (rightNode != null) ? rightNode : null;
12-
25+
return null;
1326
}
1427
}

Diff for: ‎solution/0200-0299/0235.Lowest Common Ancestor of a Binary Search Tree/Solution.py

+18
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,18 @@
1+
# Definition for a binary tree node.
2+
# class TreeNode:
3+
# def __init__(self, x):
4+
# self.val = x
5+
# self.left = None
6+
# self.right = None
7+
8+
class Solution:
9+
def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
10+
if p == q:
11+
return p
12+
while root:
13+
if root.val < p.val and root.val < q.val:
14+
root = root.right
15+
elif root.val > p.val and root.val > q.val:
16+
root = root.left
17+
else:
18+
return root

Diff for: ‎solution/0200-0299/0235.Lowest Common Ancestor of a Binary Search Tree/images/binarysearchtree_improved.png

7.48 KB
Loading

Diff for: ‎solution/0200-0299/0236.Lowest Common Ancestor of a Binary Tree/README.md

+46-5
Original file line numberDiff line numberDiff line change
@@ -10,9 +10,7 @@
1010

1111
<p>例如，给定如下二叉树:&nbsp; root =&nbsp;[3,5,1,6,2,0,8,null,null,7,4]</p>
1212

13-
<p><img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2018/12/15/binarytree.png" style="height: 190px; width: 200px;"></p>
14-
15-
<p>&nbsp;</p>
13+
![](./images/binarytree.png)
1614

1715
<p><strong>示例 1:</strong></p>
1816

@@ -42,21 +40,64 @@
4240
## 解法
4341
<!-- 这里可写通用的实现逻辑 -->
4442

43+
根据“**最近公共祖先**”的定义，若 root 是 p, q 的最近公共祖先 ，则只可能为以下情况之一：
44+
45+
- 如果 p 和 q 分别是 root 的左右节点，那么 root 就是我们要找的最近公共祖先；
46+
- 如果 p 和 q 都是 root 的左节点，那么返回 `lowestCommonAncestor(root.left, p, q)`；
47+
- 如果 p 和 q 都是 root 的右节点，那么返回 `lowestCommonAncestor(root.right, p, q)`。
48+
49+
**边界条件讨论**：
50+
51+
- 如果 root 为 null，则说明我们已经找到最底了，返回 null 表示没找到；
52+
- 如果 root 与 p 相等或者与 q 相等，则返回 root；
53+
- 如果左子树没找到，递归函数返回 null，证明 p 和 q 同在 root 的右侧，那么最终的公共祖先就是右子树找到的结点；
54+
- 如果右子树没找到，递归函数返回 null，证明 p 和 q 同在 root 的左侧，那么最终的公共祖先就是左子树找到的结点。
4555

4656
<!-- tabs:start -->
4757

4858
### **Python3**
4959
<!-- 这里可写当前语言的特殊实现逻辑 -->
5060

5161
```python
52-
62+
# Definition for a binary tree node.
63+
# class TreeNode:
64+
# def __init__(self, x):
65+
# self.val = x
66+
# self.left = None
67+
# self.right = None
68+
69+
class Solution:
70+
def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
71+
if root is None or root == p or root == q:
72+
return root
73+
left = self.lowestCommonAncestor(root.left, p, q)
74+
right = self.lowestCommonAncestor(root.right, p, q)
75+
return right if left is None else (left if right is None else root)
5376
```
5477

5578
### **Java**
5679
<!-- 这里可写当前语言的特殊实现逻辑 -->
5780

5881
```java
59-
82+
/**
83+
* Definition for a binary tree node.
84+
* public class TreeNode {
85+
* int val;
86+
* TreeNode left;
87+
* TreeNode right;
88+
* TreeNode(int x) { val = x; }
89+
* }
90+
*/
91+
class Solution {
92+
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
93+
if (root == null || root == p || root == q) {
94+
return root;
95+
}
96+
TreeNode left = lowestCommonAncestor(root.left, p, q);
97+
TreeNode right = lowestCommonAncestor(root.right, p, q);
98+
return left == null ? right : (right == null ? left : root);
99+
}
100+
}
60101
```
61102

62103
### **...**

Diff for: ‎solution/0200-0299/0236.Lowest Common Ancestor of a Binary Tree/README_EN.md

+34-10
Original file line numberDiff line numberDiff line change
@@ -13,11 +13,7 @@
1313

1414
<p>Given the following binary tree:&nbsp; root =&nbsp;[3,5,1,6,2,0,8,null,null,7,4]</p>
1515

16-
<img alt="" src="https://assets.leetcode.com/uploads/2018/12/14/binarytree.png" style="width: 200px; height: 190px;" />
17-
18-
<p>&nbsp;</p>
19-
20-
16+
![](./images/binarytree.png)
2117

2218
<p><strong>Example 1:</strong></p>
2319

@@ -60,11 +56,8 @@
6056

6157

6258
<ul>
63-
6459
<li>All of the nodes&#39; values will be unique.</li>
65-
6660
<li>p and q are different and both values will&nbsp;exist in the binary tree.</li>
67-
6861
</ul>
6962

7063

@@ -78,13 +71,44 @@
7871
### **Python3**
7972

8073
```python
81-
74+
# Definition for a binary tree node.
75+
# class TreeNode:
76+
# def __init__(self, x):
77+
# self.val = x
78+
# self.left = None
79+
# self.right = None
80+
81+
class Solution:
82+
def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
83+
if root is None or root == p or root == q:
84+
return root
85+
left = self.lowestCommonAncestor(root.left, p, q)
86+
right = self.lowestCommonAncestor(root.right, p, q)
87+
return right if left is None else (left if right is None else root)
8288
```
8389

8490
### **Java**
8591

8692
```java
87-
93+
/**
94+
* Definition for a binary tree node.
95+
* public class TreeNode {
96+
* int val;
97+
* TreeNode left;
98+
* TreeNode right;
99+
* TreeNode(int x) { val = x; }
100+
* }
101+
*/
102+
class Solution {
103+
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
104+
if (root == null || root == p || root == q) {
105+
return root;
106+
}
107+
TreeNode left = lowestCommonAncestor(root.left, p, q);
108+
TreeNode right = lowestCommonAncestor(root.right, p, q);
109+
return left == null ? right : (right == null ? left : root);
110+
}
111+
}
88112
```
89113

90114
### **...**

0 commit comments

Comments
 (0)