C++层序遍历二叉树的完整cin/cout代码

用队列去进行实现，先把根节点压入队列中，然后开始循环，每次循环时针对队首结点，将其左节点和有节点压入队列，然后队首结点就弹出，这样就可以实现对一个二叉树进行层序的遍历了。

#include <iostream>
using namespace std;
#include <string>
#include<queue>
struct TreeNode
{
    int val;
    TreeNode * left;
    TreeNode * right;
    TreeNode(int x): val(x),left(nullptr),right(nullptr){}
};
int main() {
    queue<TreeNode*> res;
    TreeNode *head = new TreeNode(1);
    TreeNode *p = head;
    head->left = new TreeNode(2);
    head->right = new TreeNode(3);
    head->left->left = new TreeNode(4);
    head->left->right = new TreeNode(5);
    head->right->left = new TreeNode(6);
    head->right->right = new TreeNode(7);
    vector<int> to_pr;
    res.push(head);
    while (!res.empty()) {
        if (res.front()->left) {
            res.push(res.front()->left);
        }
        if (res.front()->right) {
            res.push(res.front()->right);
        }
        to_pr.push_back(res.front()->val);
        res.pop();
    }
    for (int i = 0; i < to_pr.size(); i++) {
        if (i < to_pr.size() - 1) cout << to_pr[i] << "->";
        else cout << to_pr[i];
    }
    system("pause");
    return 0;
}

输出示例图片