3341=数据结构实验之二叉树二：遍历二叉树

#include <stdio.h>
#include <stdlib.h>
char s[1000];
int top;
struct node
{
    char c;
    struct node *left, *right;
};
struct node * creat()
{
    struct node * root;
    char c = s[top++];
    if(c!=',')
    {
        root = (struct node *)malloc(sizeof(struct node));
        root->c=c;
        root->left=creat();
        root->right=creat();
    }
    else
        return NULL;
    return root;
};
void mid(struct node *root)
{
    if(root)
    {
        mid(root->left);
        printf("%c",root->c);
        mid(root->right);
    }
}
void back(struct node *root)
{
    if(root)
    {
        back(root->left);
        back(root->right);
        printf("%c",root->c);
    }
}
int main()
{
    while(~scanf("%s",s))
    {
        top=0;
        struct node * root;
        root = (struct node *)malloc(sizeof(struct node));
        root=creat();
        mid(root);
        printf("\n");
        back(root);
        printf("\n");
    }
    return 0;
}