#include <stdio.h> #include <stdlib.h> // 二叉树结点的定义 struct TreeNode { int val; struct TreeNode *left; struct TreeNode *right;}; // 创建新结点 struct TreeNode *createNode(int val) { struct TreeNode *node = (struct TreeNode *)malloc(sizeof(struct TreeNode)); node->val = val; node->left = NULL; node->right = NULL; return node;} // 合并两棵二叉树 struct TreeNode *mergeTrees(struct TreeNode *t1, struct TreeNode *t2) { if (!t1 && !t2) { return NULL; } else if (!t1) { return t2; } else if (!t2) { return t1; } struct TreeNode *root = createNode(t1->val + t2->val); root->left = mergeTrees(t1->left, t2->left); root->right = mergeTrees(t1->right, t2->right); return root;} // 层次遍历二叉树 void levelOrder(struct TreeNode *root) { if (!root) { return; } // 创建队列 struct TreeNode **queue = (struct TreeNode **)malloc(sizeof(struct TreeNode *) * 1000); int front = 0, rear = 0; queue[rear++] = root; while (front < rear) { struct TreeNode *node = queue[front++]; printf("%d ", node->val); if (node->left) { queue[rear++] = node->left; } if (node->right) { queue[rear++] = node->right; } } free(queue);}int main() { struct TreeNode *t1 = createNode(1); t1->left = createNode(3); t1->right = createNode(2); t1->left->left = createNode(5); struct TreeNode *t2 = createNode(2); t2->left = createNode(1); t2->right = createNode(3); t2->left->right = createNode(4); t2->right->right = createNode(7); struct TreeNode *root = mergeTrees(t1, t2); printf("合并后的二叉树："); levelOrder(root); printf("\n"); return 0; }每一行代码都注释

好的，下面是每一行代码的注释：

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

// 二叉树结点的定义
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
};

// 创建新结点
struct TreeNode *createNode(int val) {
    struct TreeNode *node = (struct TreeNode *)malloc(sizeof(struct TreeNode));
    node->val = val;
    node->left = NULL;
    node->right = NULL;
    return node;
}

// 合并两棵二叉树
struct TreeNode *mergeTrees(struct TreeNode *t1, struct TreeNode *t2) {
    if (!t1 && !t2) {   // 如果两棵树都为空，则返回空
        return NULL;
    } else if (!t1) {   // 如果第一棵树为空，则返回第二棵树
        return t2;
    } else if (!t2) {   // 如果第二棵树为空，则返回第一棵树
        return t1;
    }
    struct TreeNode *root = createNode(t1->val + t2->val);  // 创建新结点，值为两棵树对应结点的和
    root->left = mergeTrees(t1->left, t2->left);   // 递归合并左子树
    root->right = mergeTrees(t1->right, t2->right); // 递归合并右子树
    return root;
}

// 层次遍历二叉树
void levelOrder(struct TreeNode *root) {
    if (!root) {    // 如果根节点为空，则直接返回
        return;
    }
    // 创建队列
    struct TreeNode **queue = (struct TreeNode **)malloc(sizeof(struct TreeNode *) * 1000);
    int front = 0, rear = 0;
    queue[rear++] = root;
    while (front < rear) {
        struct TreeNode *node = queue[front++];  // 出队
        printf("%d ", node->val);   // 输出结点的值
        if (node->left) {   // 如果左子树不为空，则入队
            queue[rear++] = node->left;
        }
        if (node->right) {  // 如果右子树不为空，则入队
            queue[rear++] = node->right;
        }
    }
    free(queue);    // 释放队列内存
}

int main() {
    // 创建两棵二叉树
    struct TreeNode *t1 = createNode(1);
    t1->left = createNode(3);
    t1->right = createNode(2);
    t1->left->left = createNode(5);

    struct TreeNode *t2 = createNode(2);
    t2->left = createNode(1);
    t2->right = createNode(3);
    t2->left->right = createNode(4);
    t2->right->right = createNode(7);

    // 合并两棵二叉树，并输出结果
    struct TreeNode *root = mergeTrees(t1, t2);
    printf("合并后的二叉树：");
    levelOrder(root);
    printf("\n");
    return 0;
}