110-Balanced-Binary-Tree.java

package com.coding.patterns.tree;

class BalancedBinaryTree {

    private static Pair<Boolean, Integer> dfs(TreeNode root) {
        if (root == null) {
            return new Pair<Boolean, Integer>(true, 0);
        }

        var left = dfs(root.left);
        var right = dfs(root.right);

        var balanced =
            left.getKey() &&
            right.getKey() &&
            (Math.abs(left.getValue() - right.getValue()) <= 1);

        return new Pair<Boolean, Integer>(
            balanced,
            1 + Math.max(left.getValue(), right.getValue())
        );
    }

    public static boolean isBalanced(TreeNode root) {
        return dfs(root).getKey();
    }
}