[Swift Weekly Contest 117]LeetCode965. 单值二叉树 | Univalued Binary Tree

A binary tree is univalued if every node in the tree has the same value.

Return true if and only if the given tree is univalued.

Example 1:

Input: [1,1,1,1,1,null,1]
Output: true

Example 2:

Input: [2,2,2,5,2]
Output: false

Note:

  1. The number of nodes in the given tree will be in the range [1, 100].
  2. Each node‘s value will be an integer in the range [0, 99].


如果二叉树中的每个节点都具有相同的值,则二叉树是单值的。

如果且仅当给定树为单值时返回true。

例1:

输入:[1,1,1,1,1,null,1]

输出:真

例2:

输入:[2,2,2,5,2]

输出:假

注:

  1. 给定树中的节点数将在范围[1,100]内。
  2. 每个节点的值将是一个范围[0,99]内的整数。


12 ms

 1 /**
 2  * Definition for a binary tree node.
 3  * public class TreeNode {
 4  *     public var val: Int
 5  *     public var left: TreeNode?
 6  *     public var right: TreeNode?
 7  *     public init(_ val: Int) {
 8  *         self.val = val
 9  *         self.left = nil
10  *         self.right = nil
11  *     }
12  * }
13  */
14 class Solution {
15     var s:Set<Int> = Set<Int>()
16     func isUnivalTree(_ root: TreeNode?) -> Bool {
17         s.insert(root!.val)
18         if root?.left != nil
19         {
20              isUnivalTree(root!.left)
21         }
22         if root?.right != nil
23         {
24              isUnivalTree(root!.right)
25         }
26         return s.count == 1
27     }
28 }

原文地址:https://www.cnblogs.com/strengthen/p/10201416.html

时间: 2024-10-08 16:33:44

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