c语言二叉树层序遍历

二叉树的层序遍历是一种广度优先搜索算法，它按照层的顺序遍历二叉树的节点。下面是C语言实现二叉树层序遍历的代码：

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

// 二叉树的结构体
typedef struct BTnode {
    char element;
    struct BTnode *left;
    struct BTnode *right;
} *BTnodePtr;

// 队列的结构体
typedef struct Queue {
    BTnodePtr *data;
    int front, rear;
    int maxSize;
} *QueuePtr;

// 初始化队列
QueuePtr initQueue(int maxSize) {
    QueuePtr q = (QueuePtr)malloc(sizeof(struct Queue));
    q->data = (BTnodePtr*)malloc(sizeof(BTnodePtr) * maxSize);
    q->front = q->rear = 0;
    q->maxSize = maxSize;
    return q;
}

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

// 添加元素
void enqueue(QueuePtr q, BTnodePtr x) {
    if ((q->rear + 1) % q->maxSize == q->front) {
        printf("Queue is full.\n");
        return;
    }
    q->data[q->rear] = x;
    q->rear = (q->rear + 1) % q->maxSize;
}

// 删除元素
BTnodePtr dequeue(QueuePtr q) {
    if (isEmpty(q)) {
        printf("Queue is empty.\n");
        return NULL;
    }
    BTnodePtr x = q->data[q->front];
    q->front = (q->front + 1) % q->maxSize;
    return x;
}

// 创建结点
BTnodePtr createNode(char element) {
    BTnodePtr node = (BTnodePtr)malloc(sizeof(struct BTnode));
    node->element = element;
    node->left = node->right = NULL;
    return node;
}

// 创建二叉树
BTnodePtr createTree() {
    BTnodePtr root = createNode('A');
    root->left = createNode('B');
    root->right = createNode('C');
    root->left->left = createNode('D');
    root->left->right = createNode('E');
    root->right->left = createNode('F');
    root->right->right = createNode('G');
    return root;
}

// 层次遍历
void levelOrder(BTnodePtr root) {
    QueuePtr q = initQueue(100);
    enqueue(q, root);
    while (!isEmpty(q)) {
        BTnodePtr node = dequeue(q);
        printf("%c ", node->element);
        if (node->left != NULL) {
            enqueue(q, node->left);
        }
        if (node->right != NULL) {
            enqueue(q, node->right);
        }
    }
}

// 主函数
int main() {
    BTnodePtr root = createTree();
    printf("Level order traversal of binary tree is: ");
    levelOrder(root);
    printf("\n");
    return 0;
}