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].
/**
* Definition for a binary tree node.
* public class TreeNode {
* public int val;
* public TreeNode left;
* public TreeNode right;
* public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
public class Solution {
public bool IsUnivalTree(TreeNode root) {
return Helper(root,null);
}
private bool Helper(TreeNode root,TreeNode parent){
if(root == null){
return true;
}
if(parent!=null && root.val != parent.val){
return false;
}
return Helper(root.left,root) && Helper(root.right,root);
}
}Time Complexity: O(n)
Space Complexity: O(height)
