Cracking the Coding Interview, 4 Edition - 150 Programming Interview Questions and Solutions

Solutions to Chapter 4 | Trees and Graphs
4.1 Implement a function to check if a tree is balanced. For the purposes of this question,
a balanced tree is defined to be a tree such that no two leaf nodes differ in distance
from the root by more than one.
SOLUTION
pg 54
The idea is very simple: the difference of min depth and max depth should not exceed 1,
since the difference of the min and the max depth is the maximum distance difference possible
in the tree.
1 public static int maxDepth(TreeNode root) {
2 if (root == null) {
3 return 0;
4 }
5 return 1 + Math.max(maxDepth(root.left), maxDepth(root.right));
6 }
7
8 public static int minDepth(TreeNode root) {
9 if (root == null) {
10 return 0;
11 }
12 return 1 + Math.min(minDepth(root.left), minDepth(root.right));
13 }
14
15 public static boolean isBalanced(TreeNode root){
16 return (maxDepth(root) - minDepth(root)