用C语言Write a function to print the input tree by postorder traversal, preorder traversal, inorder traversal.

好的，以下是C语言编写的打印二叉树的三种遍历方式的函数示例：

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

// 二叉树节点的定义
typedef struct TreeNode{
    int val;
    struct TreeNode* left;
    struct TreeNode* right;
}TreeNode;

// 二叉树的后序遍历
void postorderTraversal(TreeNode* root){
    if(root == NULL){
        return;
    }
    postorderTraversal(root->left);
    postorderTraversal(root->right);
    printf("%d ", root->val);
}

// 二叉树的前序遍历
void preorderTraversal(TreeNode* root){
    if(root == NULL){
        return;
    }
    printf("%d ", root->val);
    preorderTraversal(root->left);
    preorderTraversal(root->right);
}

// 二叉树的中序遍历
void inorderTraversal(TreeNode* root){
    if(root == NULL){
        return;
    }
    inorderTraversal(root->left);
    printf("%d ", root->val);
    inorderTraversal(root->right);
}

int main(){
    // 构建二叉树
    TreeNode* root = (TreeNode*)malloc(sizeof(TreeNode));
    root->val = 1;
    TreeNode* left1 = (TreeNode*)malloc(sizeof(TreeNode));
    left1->val = 2;
    TreeNode* right1 = (TreeNode*)malloc(sizeof(TreeNode));
    right1->val = 3;
    TreeNode* left2 = (TreeNode*)malloc(sizeof(TreeNode));
    left2->val = 4;
    TreeNode* right2 = (TreeNode*)malloc(sizeof(TreeNode));
    right2->val = 5;
    root->left = left1;
    root->right = right1;
    left1->left = left2;
    left1->right = right2;
    left2->left = NULL;
    left2->right = NULL;
    right2->left = NULL;
    right2->right = NULL;
    right1->left = NULL;
    right1->right = NULL;
    
    // 打印二叉树的三种遍历方式
    printf("二叉树的后序遍历：");
    postorderTraversal(root);
    printf("\n");
    printf("二叉树的前序遍历：");
    preorderTraversal(root);
    printf("\n");
    printf("二叉树的中序遍历：");
    inorderTraversal(root);
    printf("\n");
    
    return 0;
}

注意：这是一个示例函数，并不一定适用于所有的二叉树，实际应用时可能需要根据具体情况进行调整。