POJ 1577 Falling Leaves（二叉查找树）

题目链接：http://poj.org/problem?id=1577

题目大意：
二叉查找树按照叶子节点，从下往上抹去该树，给出抹除字符序列，求该二叉树，并前序打印

解题思路：
最后抹除的是根节点，把抹除的字符序列，逆序插入到一棵空的二叉查找树就是答案。

AC代码：
在这里插入图片描述

/*** @description: poj1577,告知一层层的叶子节点，求二叉查找树* @author: michael ming* @date: 2019/5/18 23:24* @modified by: */
#include <iostream>
#include <vector>
using namespace std;
struct node
{char ch;node *left, *right;node(char &ch):ch(ch),left(NULL),right(NULL){}
};
class BST
{
public:node* root;BST():root(NULL){}void insert(char &ch){node *p = root, *prev;while(p != NULL){prev = p;if(ch < p->ch)p = p->left;elsep = p->right;}if(root == NULL){root = new node(ch);return;}if(ch < prev->ch)prev->left = new node(ch);elseprev->right = new node(ch);}void del(){del(root);}void del(node* p){if(p != NULL){del(p->left);del(p->right);delete p;}}void preOrderPrint(node* p){if(p != NULL){cout << p->ch;preOrderPrint(p->left);preOrderPrint(p->right);}}
};
bool saveChToStr(string& str)
{bool flag;char ch;while(cin.get(ch)){if(ch == '*'){flag = true;break;}else if(ch == '$'){flag = false;break;}if(ch == '\n')continue;str.push_back(ch);}return flag;
}
int main()
{bool flag;do{string str;BST tree;flag = saveChToStr(str);for(int i = str.length()-1; i >= 0; --i){tree.insert(str[i]);}tree.preOrderPrint(tree.root);cout << endl;tree.del();}while(flag);return 0;
}