三种递归遍历二叉树

#include <stdio.h>
#include <stdlib.h>

typedef int ElementType;

struct BinarySearchTreeNode
{
    ElementType Element;
    struct BinarySearchTreeNode *Left;
    struct BinarySearchTreeNode *Right;
};

int BinarySearchTreePreOrder(struct BinarySearchTreeNode *TreeRoot)
{
    if(TreeRoot!=NULL)
    {
        printf("%d
",TreeRoot -> Element);
        BinarySearchTreePreOrder(TreeRoot->Left);
        BinarySearchTreePreOrder(TreeRoot->Right);
    }
    return 0;
}

int BinarySearchTreeInOrder(struct BinarySearchTreeNode *TreeRoot)
{
    if(TreeRoot!=NULL)
    {
        BinarySearchTreeInOrder(TreeRoot->Left);
        printf("%d
",TreeRoot -> Element);
        BinarySearchTreeInOrder(TreeRoot->Right);
    }
    return 0;
}

int BinarySearchTreePostOrder(struct BinarySearchTreeNode *TreeRoot)
{
    if(TreeRoot!=NULL)
    {
        BinarySearchTreePostOrder(TreeRoot->Left);
        BinarySearchTreePostOrder(TreeRoot->Right);
        printf("%d
",TreeRoot -> Element);
    }
    return 0;
}

int main()
{
//    BinarySearchTreePreOrder(TreeRoot);
//    BinarySearchTreeInOrder(TreeRoot);
    BinarySearchTreePostOrder(TreeRoot);
    return 0;
}