PAT A1115. Counting Nodes in a BST (30)

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

#include<cstdio>
#include<algorithm>
using namespace std;

const int maxn=1010;

int n;

struct node{
    int v;
    int layer;
    node *l,*r;
};
int maxh=0;
int levelcnt[maxn]={0};

node *newNode(int v){
    node *Node=new node;
    Node->v=v;
    Node->l=NULL;
    Node->r=NULL;
    return Node;
}

void insert(node *&root,int v,int l){
    if(root==NULL){
        root=newNode(v);
        root->layer=l;
        levelcnt[l]++;
        if(root->layer>maxh)maxh=root->layer;
        return;
    }
    if(v<=root->v){
        insert(root->l,v,l+1);
    }else insert(root->r,v,l+1);
}

int main(){
    node *root=NULL;
    scanf("%d",&n);
    for(int i=0;i<n;i++){
        int v;
        scanf("%d",&v);
        insert(root,v,1);
    }
    printf("%d + %d = %d",levelcnt[maxh],levelcnt[maxh-1],levelcnt[maxh]+levelcnt[maxh-1]);
    return 0;
}