Leetcode 965. Univalued Binary Tree
Posted 逆風的薔薇
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题目
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:
- The number of nodes in the given tree will be in the range
[1, 100]
. - Each node's value will be an integer in the range
[0, 99]
.
分析
1. 遍历,验证数组
2. 递归
代码
/**
* Definition for a binary tree node.
* public class TreeNode
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) val = x;
*
*/
class Solution
/*public boolean isUnivalTree(TreeNode root)
if (root == null)
return true;
if (root.left != null && root.val != root.left.val)
return false;
if (root.right != null && root.val != root.right.val)
return false;
return isUnivalTree(root.left) && isUnivalTree(root.right);
*/
public boolean isUnivalTree(TreeNode root)
if (root == null)
return true;
boolean leftRet = root.left == null || (root.val == root.left.val && isUnivalTree(root.left));
boolean rightRet = root.right == null || (root.val == root.right.val && isUnivalTree(root.right));
return leftRet && rightRet;
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