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 }