C++输出二叉树前序、中序和后序代码

好的，以下是C语言输出二叉树前序、中序、后序遍历的代码：

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

typedef struct TreeNode{
    int val;
    struct TreeNode* left;
    struct TreeNode* right;
}TreeNode;

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

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

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

int main() {
    // 构建一棵二叉树
    TreeNode* root = (TreeNode*)malloc(sizeof(TreeNode));
    root->val = 1;

    TreeNode* left = (TreeNode*)malloc(sizeof(TreeNode));
    left->val = 2;

    TreeNode* right = (TreeNode*)malloc(sizeof(TreeNode));
    right->val = 3;

    TreeNode* left_left = (TreeNode*)malloc(sizeof(TreeNode));
    left_left->val = 4;

    TreeNode* left_right = (TreeNode*)malloc(sizeof(TreeNode));
    left_right->val = 5;

    TreeNode* right_left = (TreeNode*)malloc(sizeof(TreeNode));
    right_left->val = 6;

    TreeNode* right_right = (TreeNode*)malloc(sizeof(TreeNode));
    right_right->val = 7;

    root->left = left;
    root->right = right;

    left->left = left_left;
    left->right = left_right;

    right->left = right_left;
    right->right = right_right;

    printf("前序遍历结果: ");
    preorderTraversal(root);
    printf("\n中序遍历结果: ");
    inorderTraversal(root);
    printf("\n后序遍历结果: ");
    postorderTraversal(root);
    printf("\n");

    return 0;
}

以上代码可以测试输出一棵二叉树的前序、中序和后序遍历结果。