Balancing A Binary Tree

balancedBinaryTree.js

/* Write a funciton to check to see if a binary Tree is balanced.
For the purposes of this tree, a balanced tree is defined to be a 
tree such that the heights of the subtrees of any node never differ
by more than one */

BinaryTree.prototype.isBalanced = function() {

    var checkHeight = function(current) {
        if (!current) return 0 //height = 0;

        //check to see if left side is balanced
        var leftHeight = checkHeight(current.left);
        if (leftHeight === -1) return -1;

        //check to see if right side is balanced
        var rightHeight = checkHeight(current.right);
        if (rightHeight === -1) return -1;

        //check if current node is balanced
        var heightDiff = Math.abs(leftHeight - rightHeight);
        if (heightDiff > 1)
            return -1 // not balanced
        else
            return Math.max(leftHeight, rightHeight) + 1;
    };
    return checkHeight(this.root) === -1 ? false : true;
};


//TESTS
var bt = new BinaryTree();
bt.add(10, 14, 6, 11, 18, 5, 8, 21, 7, 19);
console.log(bt);
console.log('BALANCED: ', bt.isBalanced()) //BALANCED: false;


BinaryTree.prototype.getHeight = function() {
    var recurse = function(current) {
        if (!current) return 0;
        var leftHeight = recurse(current.left) + 1;
        var rightHeight = recurse(current.right) + 1;
        return Math.max(leftHeight, rightHeight);
    };
    return recurse(this.root);
};

var height = bt.getHeight();
console.log(height); // 5