CODE 23: Balanced Binary Tree

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 ofevery node never differ by more than 1.

	public boolean isBalanced(TreeNode root) {
		// Start typing your Java solution below
		// DO NOT write main() function
		if (null == root) {
			return true;
		}
		return checkBalanced(root) != -1;
	}

	public int checkBalanced(TreeNode root) {
		if (null == root) {
			return 0;
		}
		int left = checkBalanced(root.left);
		int right = checkBalanced(root.right);

		if (left == -1 || right == -1) {
			return -1;
		}
		if (Math.abs(left - right) > 1) {
			return -1;
		} else {
			return Math.max(left, right) + 1;
		}
	}