[LeetCode] Problem 965 - Univalued Binary Tree

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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

No.1

kb8uO1.png

Input: [1,1,1,1,1,null,1]

Output: true

No.2

kb88YD.png

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].

Code

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public class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) { val = x; }
}
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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);
}