二元樹 pre、in、post

#include<stdio.h>
#include <stdlib.h>
typedef struct list
{
    int data;
    struct list *right;
    struct list *left;
} node;
typedef node *link;
link create(int n)
{
    link temp;
    temp=(link)malloc(sizeof(node));
    temp->data=n;
    temp->right=NULL;
    temp->left=NULL;
    return temp;
}
void insert(link tree,int n)
{
    link temp;
    link curr=tree;
    link parent;
    temp=(link)malloc(sizeof(node));
    temp->data=n;
    temp->right=NULL;
    temp->left=NULL;
    while(curr!=NULL)
    {
        parent=curr;
        if(curr->data>n)
            curr=curr->left;
        else
            curr=curr->right;
    }
    if(parent->data>n)
        parent->left=temp;
    else
        parent->right=temp;
}
void inorder(link tree)
{
    if(tree!=NULL)
    {
        inorder(tree->left);
        printf("%d ",tree->data);
        inorder(tree->right);
    }
}
void posorder(link tree)
{
    if(tree!=NULL)
    {
        posorder(tree->left);
        posorder(tree->right);
        printf("%d ",tree->data);
    }
}
void preorder(link tree)
{
    if(tree!=NULL)
    {
        printf("%d ",tree->data);
        preorder(tree->left);
        preorder(tree->right);
    }
}
void f(link tree)
{
     if(tree!=NULL)
    {
        f(tree->left);
        f(tree->right);
        free(tree);
    }
}
int main()
{
    link tree;
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        int i;
        int num;
        for(i=0; i<n; i++)
        {
            scanf("%d",&num);
            if(i==0)
                tree=create(num);
            else
                insert(tree,num);
        }
        inorder(tree);
        printf("\n");
        posorder(tree);
        printf("\n");
        preorder(tree);
        f(tree);
    }
}