1 package com.rui.microsoft;
 2
 3 public class Test11_MaxDistanceBST {
 4
 5     public static void main(String[] args) {
 6         Node n1 = new Node(1);
 7         Node n2 = new Node(2);
 8         Node n3 = new Node(3);
 9         Node n4 = new Node(4);
10         Node n5 = new Node(5);
11         Node n6 = new Node(6);
12         Node n7 = new Node(7);
13         Node n8 = new Node(8);
14         Node n9 = new Node(9);
15
16         n1.left = n2; n1.right = n3;
17         n2.left = n4; n2.right = n5;
18         n4.left = n6;
19         n5.right = n7;
20         n6.left = n8;
21         n7.right = n9;
22
23         int maxDistance = Test11_MaxDistanceBST.calulate(n1).dist;
24         System.out.println(maxDistance);
25     }
26
27     public static Result calulate(Node node){
28         //if current node doesn't exist
29         //then return 0 distance and -1 depth
30         if(null == node) return new Result(0, -1);
31
32         Result leftRes = calulate(node.left);
33         Result rightRes = calulate(node.right);
34
35         //First let's assume the max distance is the left node's depth + right node's depth + left single depth + right single depth
36         int maxDis = leftRes.depth + rightRes.depth + 1 + 1;
37         //Then compare it with real distance value and get the largest one
38         maxDis = max(maxDis, max(leftRes.dist, rightRes.dist));
39
40         //return the result object, whose depth value should be choosen by comparing left node's depth and right node's depth and plus one single depth value
41         return new Result(maxDis, max(leftRes.depth, rightRes.depth) + 1);
42
43     }
44
45     private static int max(int i, int j){
46         return i > j ? i:j;
47     }
48
49     static class Result{
50         int dist;
51         int depth;
52         Result(int dist, int depth){
53             this.dist = dist;
54             this.depth = depth;
55         }
56     }
57
58     static class Node {
59         int value;
60         Node left;
61         Node right;
62         public Node(int v){
63             this.value = v;
64         }
65     }
66 }