PAT--1115. Counting Nodes in a BST

pat A.1115

题解

每个结点附加一个域表示该结点所在的层次，建树的时候同时计算。
然后遍历之。

#include <iostream>#include <string>#include <algorithm>using namespace std;typedef struct node* BinTree;struct node{    int k;    int l;    BinTree left, right;    node(int _k, int _l):k(_k), l(_l), left(0), right(0){}};int n1, n2;int p = -10000;BinTree Insert(BinTree T, int k, int l){    p = max(p, l);    if(!T) T = new node(k, l);    else if(k <= T->k)        T->left = Insert(T->left, k, l + 1);    else if(k > T->k)        T->right = Insert(T->right, k, l + 1);    return T;}void traversal(BinTree T){    if(!T) return;    if(T->l == p - 1) n2++;    if(T->l == p) n1++;    traversal(T->left);    traversal(T->right);}int main(){    int n, a;    BinTree root = NULL;    cin >> n;    for(int i = 0; i < n; ++i)    {        cin >> a;        root = Insert(root, a, 1);    }    traversal(root);    cout << n1 << " + " << n2 << " = " << n1 + n2 << endl;}