创建二叉树，三种遍历方式遍历二叉树，销毁二叉树 

#include <stdio.h>
#include <stdlib.h>
 
typedef struct Node {
    int data;
    struct Node *left;
    struct Node *right;
} Node, *Tree;
 
// 创建二叉树
Tree createTree() {
    Node *root = (Node*)malloc(sizeof(Node));
    root->data = 1;
    root->left = NULL;
    root->right = NULL; 
    return root;
}
 
// 前序遍历二叉树
void preOrderTraversal(Tree root) {
    if (root == NULL) return;
    printf("%d ", root->data);
    preOrderTraversal(root->left);
    preOrderTraversal(root->right);
}
 
// 中序遍历二叉树
void inOrderTraversal(Tree root) {
    if (root == NULL) return;
    inOrderTraversal(root->left);
    printf("%d ", root->data);
    inOrderTraversal(root->right);
}
 
// 后序遍历二叉树
void postOrderTraversal(Tree root) {
    if (root == NULL) return;
    postOrderTraversal(root->left);
    postOrderTraversal(root->right);
    printf("%d ", root->data);
}
 
// 销毁二叉树
void destroyTree(Tree root) {
    if (root == NULL) return;
    destroyTree(root->left);
    destroyTree(root->right);
    free(root);
}
 
int main() {
    Tree root = createTree();
 
    printf("Preorder traversal: ");
    preOrderTraversal(root);
    printf("\n");
 
    printf("Inorder traversal: ");
    inOrderTraversal(root);
    printf("\n");
 
    printf("Postorder traversal: ");
    postOrderTraversal(root);
    printf("\n");
 
    destroyTree(root);
 
    return 0;
}