中序+先序 建立二叉树算法（递归）

// test14.cpp : Defines the entry point for the console application.//// test13.cpp : Defines the entry point for the console application.//#include "stdafx.h"#include <iostream>using namespace std;typedef struct node {char data;struct node * l_child, * r_child;}node,* p_node ;void pre_order(p_node root){if(root){cout<<root->data<<" ";pre_order(root->l_child);pre_order(root->r_child);}}p_node advanced_create_tree(char * pre_order,char * mid_order ,int length){if(!length)return NULL; //长度为0，返回空值p_node root=new node ; //建立根节点root->data=* pre_order;char * mid_place=strchr(mid_order,* pre_order); //找到根节点在中根遍历中的位置if(!mid_place){cout<<"error happened !"<<endl;return NULL;}int l_length=strlen(mid_order)-strlen(mid_place); //左子树的长度int r_length=length-l_length-1; //右子树的长度,后面减的1为根节点root->l_child=advanced_create_tree(pre_order+1,mid_order,l_length); //递归建立根节点的左子树root->r_child=advanced_create_tree(pre_order+l_length+1,mid_place+1,r_length); //递归建立根节点的右子树return root;}//通过参数传递的建树算法void advanced_create_tree(p_node & root,char * pre_order, char * mid_order,int length){if(!length){root=NULL;return; //此处的return是必须的，必须得返回，相当于递归中的返回条件！！！！}root=new node;root->data=* pre_order;char * root_place=strchr(mid_order,* pre_order);if(!root_place)cout<<"error happened!"<<endl; int l_length=strlen(mid_order)-strlen(root_place);int r_length=length-l_length-1;advanced_create_tree(root->l_child,pre_order+1,mid_order,l_length);advanced_create_tree(root->r_child,pre_order+l_length+1,root_place+1,r_length);}void destory_tree(p_node& root){ //指针的递归撤销if(root){destory_tree(root->l_child);destory_tree(root->r_child);free(root);root=NULL; //前面使用的引用才使得此处对指针有效的赋值！！！}}int count_node(p_node root){//计算总结点数目if(!root) return 0;if(!root->l_child && !root->r_child) return 1;if(root->l_child && root->l_child) return count_node(root->l_child)+count_node(root->r_child)+1;else if(root->l_child) return count_node(root->l_child)+1;else return count_node(root->r_child)+1;}int count_leaf_node(p_node root){//计算叶子节点数if(!root) return 0;if(!root->l_child && !root->r_child)return 1;if(root->l_child && root->r_child) return count_leaf_node(root->l_child)+count_leaf_node(root->r_child);else if(root->l_child)return count_leaf_node(root->l_child);else return count_leaf_node(root->r_child);}void main(int argc, char* argv[]){char pre[] = "abdeijcfg"; char mid[] = "dbiejafcg";p_node root;advanced_create_tree(root,pre,mid,9);pre_order(root);destory_tree(root);// p_node root=advanced_create_tree(pre,mid,9);pre_order(root);}