110.balanced-binary-tree.java

/*
 * @lc app=leetcode id=110 lang=java
 *
 * [110] Balanced Binary Tree
 *
 * https://leetcode.com/problems/balanced-binary-tree/description/
 *
 * algorithms
 * Easy (40.38%)
 * Total Accepted:    305.9K
 * Total Submissions: 753K
 * Testcase Example:  '[3,9,20,null,null,15,7]'
 *
 * Given a binary tree, determine if it is height-balanced.
 *
 * For this problem, a height-balanced binary tree is defined as:
 *
 *
 * a binary tree in which the depth of the two subtrees of every node never
 * differ by more than 1.
 *
 *
 * Example 1:
 *
 * Given the following tree [3,9,20,null,null,15,7]:
 *
 *
 * ⁠   3
 * ⁠  / \
 * ⁠ 9  20
 * ⁠   /  \
 * ⁠  15   7
 *
 * Return true.
 *
 * Example 2:
 *
 * Given the following tree [1,2,2,3,3,null,null,4,4]:
 *
 *
 * ⁠      1
 * ⁠     / \
 * ⁠    2   2
 * ⁠   / \
 * ⁠  3   3
 * ⁠ / \
 * ⁠4   4
 *
 *
 * Return false.
 *
 */
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
  private boolean isBalanced = true;

  public boolean isBalanced(TreeNode root) {
    getDepth(root);
    return isBalanced;
  }

  public int getDepth(TreeNode root) {
    if (root == null) {
      return 0;
    }
    int left = getDepth(root.left);
    int right = getDepth(root.right);
    if (Math.abs(left - right) > 1) {
      isBalanced = false;
    }
    return left > right ? left + 1 : right + 1;
  }
}