二叉树前序,中序，后序遍历

#define MAX_ARRAY_SIZE 21
int array[MAX_ARRAY_SIZE] = {1,2,4,8,0,0,9,0,0,5,10,0,0,0,3,6,0,0,7,0,0};
static int index = 0;

typedef struct binary_tree_t
{
    int data;
    struct binary_tree_t *left;
    struct binary_tree_t *right;
}binary_tree;

struct binary_tree_t *create_binary_tree()
{
    if(array[index] == 0)
    {
        ++index;
        return NULL;
    }

    struct binary_tree_t *node = (struct binary_tree_t *)malloc(sizeof(struct binary_tree_t));
    if(node == NULL)
    {
        exit(1);
    }

    node->data = array[index++];
    node->left = create_binary_tree();
    node->right = create_binary_tree();

    return node;
}

void visit(struct binary_tree_t *node)
{
    printf("%d ",node->data);
}


void pre_traverse(struct binary_tree_t *root)
{
    if(root == NULL) return ;

    visit(root);

    pre_traverse(root->left);
    pre_traverse(root->right);
}

void mid_traverse(struct binary_tree_t *root)
{
    if(root == NULL) return;

    mid_traverse(root->left);
    visit(root);
    mid_traverse(root->right);
}

void order_traverse(struct binary_tree_t *root)
{
    if(root == NULL) return;

    order_traverse(root->left);
    order_traverse(root->right);

    visit(root);
}