_965.java

package com.fishercoder.solutions;

import com.fishercoder.common.classes.TreeNode;

/**
 * 965. 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:
 *
 *         1
 *        / \
 *       1   1
 *      / \   \
 *     1  1   1
 *
 * Input: [1,1,1,1,1,null,1]
 * Output: true
 *
 *
 * Example 2:
 *        2
 *       / \
 *      2   2
 *     / \
 *    5  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].
 */
public class _965 {
  public static class Solution1 {
    public boolean isUnivalTree(TreeNode root) {
      if (root == null) {
        return true;
      }
      return dfs(root, root.val);
    }

    private boolean dfs(TreeNode root, int value) {
      if (root == null) {
        return true;
      }
      if (root.val != value) {
        return false;
      }
      return dfs(root.left, value) && dfs(root.right, value);
    }
  }
}