L110. Balanced Binary Tree

Binary Tree

Problem:

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 left and right subtrees of every node differ in height by no more than 1.

Example 1:

Given the following tree [3,9,20,null,null,15,7]:

    3
   / \
  9  20
    /  \
   15   7

Return true.

Solution:

public boolean isBalanced(TreeNode root){
    if(root == null) return true;
    int left = getHeight(root.left);
    int right = getHeight(root.right);
    return Math.abs(left - right) <= 1 && isBalanced(root.left) && isBalanced(root.right); 
}
private int getHeight(TreeNode root){
    if(root == null) return 0;
    int leftHeight = getHeight(root.left);
    int rightHeight = getHeight(root.right);
    return Math.max(leftHeight, rightHeight) + 1;
}