110. Balanced Binary Tree Leetcode Java

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.

Solution:

The 3 requirements for a balanced tree are:

1. left subtree is balanced

2. right subtree is balanced

3. the depth of two subtrees differ by no more than 1

Tips:

When the tree is not balanced, return -1 rather than the real depth in the helper method. 

  public boolean isBalanced(TreeNode root) {  
     return getDepth(root)>=0;  
   }  
   public int getDepth(TreeNode root){  
     if(root==null) return 0;  
     int leftD=getDepth(root.left);  
     int rightD=getDepth(root.right);  
     if(leftD<0 || rightD<0 || Math.abs(leftD-rightD)>1) return -1;  
     return Math.max(leftD,rightD)+1;  
   }