面试题5：计算二叉树中最大节点到最小节点之间的距离

网易2016实习研发工程师编程题

有一棵二叉树，树上每个点标有权值，权值各不相同，请设计一个算法算出权值最大的叶节点到权值最小的叶节点的距离。二叉树每条边的距离为1，一个节点经过多少条边到达另一个节点为这两个节点之间的距离。

给定二叉树的根节点root，请返回所求距离。

 1 #include <iostream>
 2 #include <climits>
 3 //struct ListNode {
 4 //    int val;
 5 //    ListNode* next;
 6 //    ListNode() :
 7 //            val(0), next(nullptr) {
 8 //    }
 9 //    ListNode(int x) :
10 //            val(x), next(nullptr) {
11 //    }
12 //};
13 
14 struct TreeNode {
15     int val;
16     TreeNode* left;
17     TreeNode* right;
18     TreeNode() :
19             val(0), left(nullptr), right(nullptr) {
20     }
21     TreeNode(int x) :
22             val(x), left(nullptr), right(nullptr) {
23     }
24 };
25 
26 class Solution {
27 private:
28     TreeNode* maxNode = new TreeNode(INT_MIN);
29     TreeNode* minNode = new TreeNode(INT_MAX);
30 private:
31     TreeNode* getLCANode(TreeNode* root, TreeNode* p, TreeNode* q) {
32         if (root == nullptr || root == p || root == q) {
33             return root;
34         }
35         TreeNode* left = getLCANode(root->left, p, q);
36         TreeNode* right = getLCANode(root->right, p, q);
37         if (left && right) {
38             return root;
39         }
40         if (left == nullptr)
41             return right;
42         else // right == nullptr;
43             return left;
44     }
45 
46     void getMaxMinNode(TreeNode* root){
47         if(root==nullptr) return;
48         if(root->val > maxNode->val){
49             maxNode = root;
50         }
51         if(root->val < minNode->val){
52             minNode = root;
53         }
54         getMaxMinNode(root->left);
55         getMaxMinNode(root->right);
56     }
57 
58     //get distance between maxNode or minNode and LCAnode
59     int getDis(TreeNode* LCANode,TreeNode* node){
60         if(LCANode == nullptr) return -1;
61         if(LCANode->val == node->val)
62             return 0;
63         int dis = getDis(LCANode->left,node);
64         if(dis == -1){
65             dis = getDis(LCANode->right,node);
66         }
67         if(dis != -1){
68             return dis + 1;
69         }
70         return -1;
71     }
72 public:
73     int getMaxMinNodeDis(TreeNode* root){
74         if(root == nullptr) return 0;
75         getMaxMinNode(root);
76         TreeNode* LCANode = getLCANode(root,maxNode,minNode);
77         int a = getDis(LCANode,maxNode);
78         int b = getDis(LCANode,minNode);
79         return a+b;
80     }
81 };

 

posted @ 2017-05-12 22:36  wxquare  阅读(1329)  评论(0)  编辑  收藏  举报