从上到下按层打印二叉树，同一层结点从左至右输出。每一层输出一行。

// test20.cpp : 定义控制台应用程序的入口点。
//

include "stdafx.h"

include

include

include

include

include

using namespace std;

struct TreeNode {
int val;
struct TreeNode left;
struct TreeNode right;
TreeNode(int x) :
val(x), left(NULL), right(NULL) {
}
};
class Solution {
public:
//设置两个队列，一个存放父节点；一个存放子节点;打印完父节点后，再把子队列的值存放到父队列中
vector<vector > Print(TreeNode pRoot) {
queue<TreeNode> faQue;
queue<TreeNode> chQue;
vector<vector> vec;
vector line;
if (pRoot == NULL) return{};
faQue.push(pRoot);
/line.push_back(pRoot->val);
vec.push_back(line);*/

while (!faQue.empty ()||!chQue.empty ())
{
if (faQue.front()->left != NULL) chQue.push(faQue.front()->left); //左右节点放到孩子节点的位置
if (faQue.front()->right != NULL) chQue.push(faQue.front()->right);
line.push_back(faQue.front()->val);
faQue.pop();
if (faQue.empty())//当节点打印完成后，将所有父节点的值传递过去；要清空line；把孩子的节点给父节点；子队列清空；进行下次循环；
{
vec.push_back(line);
line.clear();
while (!chQue.empty ())
{
faQue.push(chQue.front());
chQue.pop();
}
}
}
return vec;

}

void preCreate(TreeNode* &T)
{
int num;
cin >> num;
if (num == 0) T = NULL;
else
{
T = new TreeNode(num);
preCreate(T->left);
preCreate(T->right);
}
}

void preOrder(TreeNode* T)
{
if (T == NULL) return;
else
{
cout << T->val << " ";
preOrder(T->left);
preOrder(T->right);
}
}
};
int main()
{

Solution so;
TreeNode *T1;
TreeNode *T2;
vector<vector> vec;

cout << "创建T1:" << endl;
so.preCreate(T1);
cout << "创建T1成功！" << endl;

cout << "T1的前序遍历:" << endl;
so.preOrder(T1);
cout << endl;

//so.CreateImageTree(T1,T2);
//cout << "T2的前序遍历是（T2是T1的镜像）："<<endl;
//so.preOrder(T2);
//cout << endl;

cout << "T1的层次关系是："<<endl ;
vec = so.Print(T1);
for (auto it = vec.begin();it != vec.end();++it)
{
for (auto p = it->begin();p != it->end();++p)
{
cout << *p << " ";
}
cout << endl;
}

cout << endl;
return 0;
}