二叉树链式存储结构下的创建及遍历算法

#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#define MAX 100

char * p;
typedef struct BTree{
    char * str;
    struct BTree * lchild;
    struct BTree * rchild;
}BTree;

BTree* creat_tree(){
    BTree* temp;
    while(*p==' ')p++;
    if(*p=='#'){
        p++;
        return NULL;
    }
    if(*p!=' '){
        int i=0;
        temp = (BTree *)malloc(sizeof(BTree));
        temp->str[i++]=*p++;
        temp->lchild=creat_tree();
        temp->rchild=creat_tree();
    }
    return temp;
}

void pre_visit(BTree* node){
    printf("%c",node->str);
    if(node->lchild!=NULL)pre_visit(node->lchild);
    if(node->rchild!=NULL)pre_visit(node->rchild);
}
int main()
{
    char tree[MAX];p=tree;
    BTree * head;
    printf("Please input the tree(use char and #)
要求按照先序遍历的方式输入，加上#进行区分
例如123# #4##5##:
");
    //scanf("%s",tree);
    gets(tree);

    if(*p!=''&&*p!=' '&&*p!='#'){
        head=(BTree *)malloc(sizeof(BTree));
        int i=0;
        head->str[i++]=*p++;
        //printf("head is %c",head->str);
        head->lchild=creat_tree();
        head->rchild=creat_tree();
    }

    printf("tree is :
");
    pre_visit(head);
    return 0;
}