c++二叉树的层序遍历

二叉树的层序遍历可以使用队列来实现。具体步骤如下：

1. 首先创建一个队列，将根节点入队
2. 当队列不为空时，依次出队队首元素，并将其左右子节点入队
3. 将出队的节点值存储到结果数组中
4. 重复执行步骤2和步骤3，直到队列为空

以下是 C++ 代码实现：

#include <iostream>
#include <queue>

using namespace std;

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

void levelOrder(TreeNode* root) {
    if (root == NULL) {
        return;
    }
    queue<TreeNode*> q;
    q.push(root);
    while (!q.empty()) {
        TreeNode* curr = q.front();
        q.pop();
        cout << curr->val << " ";
        if (curr->left != NULL) {
            q.push(curr->left);
        }
        if (curr->right != NULL) {
            q.push(curr->right);
        }
    }
}

int main() {
    TreeNode* root = new TreeNode(1);
    root->left = new TreeNode(2);
    root->right = new TreeNode(3);
    root->left->left = new TreeNode(4);
    root->left->right = new TreeNode(5);
    root->right->left = new TreeNode(6);
    root->right->right = new TreeNode(7);

    levelOrder(root);

    return 0;
}

输出结果为：1 2 3 4 5 6 7