1115. Counting Nodes in a BST (30)（建立二叉搜索树）

1. Counting Nodes in a BST (30)

时间限制
400 ms
内存限制
65536 kB
代码长度限制
16000 B
判题程序
Standard
作者
CHEN, Yue
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 [-1000 1000] 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

找出一个二叉搜索树的倒数第一层的节点数，和倒数第二层的节点数

#include<iostream>#include<cstdio>using namespace std;int lev[2000];int maxlev=1;int n;struct tree{int key;struct tree *left,*right;};struct tree * creat (struct tree *now ,int num,int level){    if (now==NULL)    {        now =new struct tree();        now->key=num;        now->left=NULL;        now->right=NULL;        lev[level]++;        maxlev=max(maxlev,level);    }    else    {        if (num<=now->key)        {            now->left=creat(now->left,num,level+1);        }        else        {            now->right=creat(now->right,num,level+1);        }    }    return now;}int main(){    cin>>n;    struct tree *first=NULL;    int num;    for (int i=0;i<n;i++)    {        cin>>num;        first= creat(first,num,1);    }    printf("%d + %d = %d",lev[maxlev],lev[maxlev-1],lev[maxlev]+lev[maxlev-1]);    return 0;}