PAT Advanced 1115 【Counting Nodes in a BST】（30 ）

分析：再树的存储里加上当前层数，建完树用dfs遍历即可。

#include<iostream>
#include<cstdio>
using namespace std;
struct Node{
	int v, lev;
	struct Node *l, *r;
};
int maxlev, n1, n2;
Node *insert(Node *root, int v, int lev){
	if(!root){
		root = new Node;
		root->v = v;
		root->l = root->r = NULL;
		root->lev = lev;
		maxlev = max(maxlev, lev);
	} else {
		if(v > root->v){
			root->r = insert(root->r, v, lev+1);
		} else {
			root->l = insert(root->l, v, lev+1);
		}
	}
	return root;
}
void dfs(Node *root){
	if(!root) return;
	if(root->lev == maxlev) n1++;
	else if(root->lev == maxlev-1) n2++;
	dfs(root->l);
	dfs(root->r);
}
int main(){
//	freopen("aa.txt", "r", stdin);
	int n, tem;
	cin >> n;
	Node *root = NULL;
	for(int i = 0; i<n; i++){
		cin >> tem;
		root = insert(root, tem, 1);
	}
	dfs(root);
	cout << n1 << " + " << n2 << " = " << n1+n2 << '\n';
	return 0;
}