根据前序遍历和中序遍历建立二叉树，并后序遍历输出以及交换左右子树后输出，请修改下面代码

#include <stdio.h>
#include <malloc.h>
#include <string.h>
#define maxsize 50

typedef struct Bnode
{
    char data;
    struct Bnode *Lchild, *Rchild;
}BTnode, *BTptr;

BTptr CreateBT(char *pre_str, char *in_str)
{
    BTptr bt;
    bt=(BTptr)malloc(sizeof(BTnode));
    bt->data=pre_str[0];
    bt->Lchild=NULL;
    bt->Rchild=NULL;
    if(strlen(pre_str)==1)
        return bt;
    else
    {
        char pre_left[maxsize];
        char in_left[maxsize];
        char pre_right[maxsize];
        char in_right[maxsize];
        int i=0, j=0;
        while(in_str[i]!=bt->data)
        {
            pre_left[i]=pre_str[i+1];
            in_left[i]=in_str[i];
            i++;
        }
        pre_left[i]='\0';
        in_left[i]='\0';
        while(i<=strlen(in_str))
        {
            pre_right[j]=pre_str[i];
            in_right[j]=in_str[i+1];
            i++;j++;
        }
        pre_right[j]='\0';
        in_right[j]='\0';
        if(strlen(pre_left)!=strlen(in_left) || strlen(pre_right)!=strlen(in_right))
        {
            printf("Error\n");
            return 0;
        }
        bt->Lchild=CreateBT(pre_left, in_left);
        bt->Rchild=CreateBT(pre_right, in_right);
        return bt;
    }
}

BTptr Judge(char *pre_str, char *in_str)
{
    if(pre_str==NULL || in_str==NULL || strlen(pre_str)!=strlen(in_str))
        return 0;
    else
        return CreateBT(pre_str, in_str);
}

void PreExchange(BTptr T)
{
    BTptr p;
    if(T!=NULL)
    {
        p=T->Lchild;
        T->Lchild=T->Rchild;
        T->Rchild=p;
        PreExchange(T->Lchild);
        PreExchange(T->Rchild);
    }
}

void PostOrderBT(BTptr T)
{
    if(T!=NULL)
    {
        PostOrderBT(T->Lchild);
        PostOrderBT(T->Rchild);
        printf("%c",T->data);
    }
}

void main()
{
    char pre_str[maxsize];
    char in_str[maxsize];
    gets(pre_str);
    gets(in_str);
    BTptr bt;
    bt=Judge(pre_str, in_str);
    PostOrderBT(bt);
    printf("\n");
    PreExchange(bt);
    PostOrderBT(bt);
}

改好了：
#include
#include
#include
#define maxsize 50

typedef struct Bnode
{
char data;
struct Bnode *Lchild, *Rchild;
}BTnode, *BTptr;

BTptr CreateBT(char *pre_str, char *in_str)
{
BTptr bt;
bt=(BTptr)malloc(sizeof(BTnode));
bt->data=pre_str[0];
bt->Lchild=NULL;
bt->Rchild=NULL;
if(strlen(pre_str)==0)
return bt;

if(strlen(pre_str)==1)
    return bt;
else
{
    char pre_left[maxsize];
    char in_left[maxsize];
    char pre_right[maxsize];
    char in_right[maxsize];
    int i=0, j=0;
    while(in_str[i]!=bt->data)
    {
        pre_left[i]=pre_str[i+1];
        in_left[i]=in_str[i];
        i++;
    }
    pre_left[i]='\0';
    in_left[i]='\0';

    while(i<(int)strlen(in_str))//动了下
    {
        pre_right[j]=pre_str[i+1];//[i]改为[i+1]
        in_right[j]=in_str[i+1];
        i++;j++;
    }
    pre_right[j]='\0';
    in_right[j]='\0';
    if(strlen(pre_left)!=strlen(in_left) || strlen(pre_right)!=strlen(in_right))
    {
        printf("Error\n");
        return 0;
    }
    bt->Lchild=CreateBT(pre_left, in_left);
    bt->Rchild=CreateBT(pre_right, in_right);
    return bt;
}

}

BTptr Judge(char *pre_str, char *in_str)
{
if(pre_str==NULL || in_str==NULL || strlen(pre_str)!=strlen(in_str))
return 0;
else
return CreateBT(pre_str, in_str);
}

void PreExchange(BTptr T)
{
BTptr p;
if(T!=NULL)
{
p=T->Lchild;
T->Lchild=T->Rchild;
T->Rchild=p;
PreExchange(T->Lchild);
PreExchange(T->Rchild);
}
}

void PostOrderBT(BTptr T)
{
if(T!=NULL)
{
PostOrderBT(T->Lchild);
PostOrderBT(T->Rchild);
printf("%c",T->data);
}
}

void main()
{
char pre_str[maxsize];
char in_str[maxsize];
gets(pre_str);
gets(in_str);
BTptr bt;
bt=Judge(pre_str, in_str);
PostOrderBT(bt);
printf("\n");
PreExchange(bt);
PostOrderBT(bt);
}