完全二叉树的层序遍历C语言

完全二叉树是一种特殊的二叉树，它除了最后一层节点可能不满外，其他每一层的节点数都达到了最大值。层序遍历是指从根节点开始，按照从上到下、从左到右的顺序遍历每个节点。以下是完全二叉树层序遍历的C语言代码实现：

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

// 定义二叉树结构体
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
};

// 定义队列结构体
struct QueueNode {
    struct TreeNode *node;
    struct QueueNode *next;
};

// 初始化队列
struct QueueNode* initQueue() {
    struct QueueNode *queue = (struct QueueNode*)malloc(sizeof(struct QueueNode));
    queue->next = NULL;
    return queue;
}

// 入队操作
void enQueue(struct QueueNode *queue, struct TreeNode *node) {
    struct QueueNode *temp = (struct QueueNode*)malloc(sizeof(struct QueueNode));
    temp->node = node;
    temp->next = NULL;
    while (queue->next != NULL) {
        queue = queue->next;
    }
    queue->next = temp;
}

// 出队操作
struct TreeNode* deQueue(struct QueueNode *queue) {
    struct QueueNode *temp = queue->next;
    struct TreeNode *res = temp->node;
    queue->next = temp->next;
    free(temp);
    return res;
}

// 层序遍历
void levelOrder(struct TreeNode* root) {
    if (root == NULL) {
        return;
    }
    struct QueueNode *queue = initQueue();
    enQueue(queue, root);
    while (queue->next != NULL) {
        struct TreeNode *temp = deQueue(queue);
        printf("%d ", temp->val);
        if (temp->left != NULL) {
            enQueue(queue, temp->left);
        }
        if (temp->right != NULL) {
            enQueue(queue, temp->right);
        }
    }
}

int main() {
    // 创建一个完全二叉树
    struct TreeNode *root = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->val = 1;
    root->left = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->left->val = 2;
    root->right = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->right->val = 3;
    root->left->left = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->left->left->val = 4;
    root->left->right = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->left->right->val = 5;
    root->right->left = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->right->left->val = 6;

    // 调用层序遍历函数
    levelOrder(root);

    return 0;
}