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 (≤1000) which is the size of the input sequence. Then given in the next line are the N integers in [−10001000] 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
#include<iostream> //建立二叉树和dfs
using namespace std;
int maxdeep=0, a=0, b=0;
struct node{
int value;
node* left=NULL;
node* right=NULL;
node(int v):value(v), left(NULL), right(NULL){
}
};
node* insert(int v, node* root, int deep){
if(!root){
node* temp=new node(v);
root =temp;
maxdeep=(deep>maxdeep?deep:maxdeep);
}else{
if(v<=root->value)
root->left=insert(v, root->left, deep+1);
else
root->right=insert(v, root->right, deep+1);
}
return root;
}
void preorder(node* root, int deep){
if(root==NULL)
return;
if(deep==maxdeep-1)
a++;
else if(deep==maxdeep)
b++;
preorder(root->left, deep+1);
preorder(root->right, deep+1);
}
int main(){
int n, v;
cin>>n;
node* root=NULL;
for(int i=0; i<n; i++){
cin>>v;
root=insert(v, root, 1);
}
preorder(root, 1);
cout<<b<<" + "<<a<<" = "<<a+b<<endl;
return 0;
}