二叉树层序遍历c语言代码

下面是二叉树层序遍历的 C 语言代码实现：

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

#define MAX_QUEUE_SIZE 100 // 队列最大容量

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

typedef struct Queue {
    TreeNode *data[MAX_QUEUE_SIZE];
    int front, rear;
} Queue;

// 初始化队列
void init(Queue *q) {
    q->front = q->rear = 0;
}

// 判断队列是否为空
int is_empty(Queue *q) {
    return q->front == q->rear;
}

// 入队
void enqueue(Queue *q, TreeNode *node) {
    if ((q->rear + 1) % MAX_QUEUE_SIZE == q->front) {
        printf("Queue is full.\n");
        return;
    }
    q->data[q->rear] = node;
    q->rear = (q->rear + 1) % MAX_QUEUE_SIZE;
}

// 出队
TreeNode *dequeue(Queue *q) {
    if (is_empty(q)) {
        printf("Queue is empty.\n");
        return NULL;
    }
    TreeNode *node = q->data[q->front];
    q->front = (q->front + 1) % MAX_QUEUE_SIZE;
    return node;
}

// 层序遍历
void level_order(TreeNode *root) {
    if (root == NULL) return;

    Queue q;
    init(&q);
    enqueue(&q, root);

    while (!is_empty(&q)) {
        TreeNode *node = dequeue(&q);
        printf("%d ", node->val);

        if (node->left != NULL) enqueue(&q, node->left);
        if (node->right != NULL) enqueue(&q, node->right);
    }
}

int main() {
    // 构建二叉树
    TreeNode *root = (TreeNode *)malloc(sizeof(TreeNode));
    root->val = 1;

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

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

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

    root->right->left = (TreeNode *)malloc(sizeof(TreeNode));
    root->right->left->val = 4;

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

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

    // 层序遍历
    level_order(root);

    return 0;
}

输出结果为：1 2 3 4 5