1115. Counting Nodes in a BST (30) 二叉树

题目地址

创建二叉搜索树并输出其最低两层的节点数目，使用先序遍历，注意当树只有一层时的情况。

//// Created by aleafall on 16-10-3.//#include<iostream>#include<map>using namespace std;struct Node {    int data;    Node *lchild, *rchild;} *root;map<int, int> mp;void preOrder(Node *root, int depth) {    if (root == NULL) return;    if (mp.find(depth) != mp.end()) mp[depth]++;    else mp[depth] = 1;    preOrder(root->lchild, depth + 1);    preOrder(root->rchild, depth + 1);}void insert(Node *&root, int data) {    if (root == NULL) {        root = new Node;        root->data = data;        root->lchild = root->rchild = NULL;        return;    }    if (data <= root->data) insert(root->lchild, data);    else insert(root->rchild, data);}int main() {    int n, x;    cin >> n;    for (int i = 0; i < n; i++) {        cin >> x;        insert(root, x);    }    preOrder(root, 1);    int n1, n2;    if (mp.size() > 1) {        map<int, int>::iterator it = --mp.end();        n1 = it->second;        n2 = (--it)->second;    } else {        n1 = 1;        n2 = 0;    }    cout << n1 << " + " << n2 << " = " << n1 + n2 << endl;    return 0;}