A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties:
- The left subtree of a node contains only nodes with keys less than or equal to the node's key.
- The right subtree of a node contains only nodes with keys greater than the node's key.
- Both the left and right subtrees must also be binary search trees.
Insert a sequence of numbers into an initially empty binary search tree. Then you are supposed to count the total number of nodes in the lowest 2 levels of the resulting tree.
Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer N (≤) which is the size of the input sequence. Then given in the next line are the N integers in [ which are supposed to be inserted into an initially empty binary search tree.
Output Specification:
For each case, print in one line the numbers of nodes in the lowest 2 levels of the resulting tree in the format:
n1 + n2 = n
where n1 is the number of nodes in the lowest level, n2 is that of the level above, and n is the sum.
Sample Input:
9 25 30 42 16 20 20 35 -5 28
Sample Output:
2 + 4 = 6就是一个建树的问题，不值30分
1 #include <bits/stdc++.h>
2 using namespace std;
3 struct Node{
4 int val;
5 Node *left, *right;
6 };
7 int n, x, vis[2000];
8 int maxl = 0;
9 Node *build(Node *root, int val){
10 if(root == NULL){
11 root = new Node();
12 root->val = val;
13 root->left = root->right = NULL;
14 }else{
15 if(val <= root->val){
16 root->left = build(root->left, val);
17 }else{
18 root->right = build(root->right, val);
19 }
20 }
21 return root;
22 }
23 void output(Node *root, int x){
24 if(root != NULL){
25 vis[x]++;
26 maxl = max(maxl,x);
27 output(root->left, x+1);
28 output(root->right, x+1);
29 }
30 }
31 int main(){
32 cin >> n;
33 Node *tree = NULL;
34 for(int i = 0; i < n; i++){
35 cin >> x;
36 tree = build(tree,x);
37 }
38 output(tree, 1);
39 cout << vis[maxl] <<" + "<<vis[maxl-1]<<" = "<<vis[maxl]+vis[maxl-1]<<endl;
40 return 0;
41 }