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235_lowest_common_ancestor_of_a_binary_search_tree.go
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235_lowest_common_ancestor_of_a_binary_search_tree.go
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/*
Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.
According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself).”
Given binary search tree: root = [6,2,8,0,4,7,9,null,null,3,5]
Example 1:
Input: root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 8
Output: 6
Explanation: The LCA of nodes 2 and 8 is 6.
Example 2:
Input: root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 4
Output: 2
Explanation: The LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself according to the LCA definition.
Note:
All of the nodes' values will be unique.
p and q are different and both values will exist in the BST.
*/
package main
/**
* Definition for TreeNode.
* type TreeNode struct {
* Val int
* Left *ListNode
* Right *ListNode
* }
*/
/*
#### 解题思路
- 如果p,q都小于当前节点,说明在当前节点的左子树
- 如果p,q都大于当前节点,说明在当前节点的右子树
- 如果一个大一个小,说明当前节点即为公共祖先节点
*/
func lowestCommonAncestor(root, p, q *TreeNode) *TreeNode {
if p.Val > root.Val && q.Val > root.Val {
return lowestCommonAncestor(root.Right, p, q)
} else if p.Val < root.Val && q.Val < root.Val {
return lowestCommonAncestor(root.Left, p, q)
}
return root
}