《剑指offer》面试题19——二叉树的镜像（C++）

操作给定的二叉树，将其变换为源二叉树的镜像。

递归思想。

代码：

#include<iostream>
#include <vector>
#include <queue>

using namespace std;

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

void Mirror(TreeNode *pRoot)   //核心代码
{
    if(pRoot==NULL)    //空树
        return;
    if(pRoot->left==NULL&&pRoot->right==NULL)   //只有一个结点的二叉树
        return;

    TreeNode* pTemp=pRoot->left;   //创建一个临时结点指针，用于交换左右子节点
    pRoot->left=pRoot->right;
    pRoot->right=pTemp;                  //交换根节点的左右结点

    if(pRoot->left!=NULL)
        Mirror(pRoot->left);
    if(pRoot->right!=NULL)
        Mirror(pRoot->right);

}


class BinTree
{
public:
    TreeNode *root;
    TreeNode* CreateTree();
    void preOrder(TreeNode *r);//递归实现先序遍历
    void InOrder(TreeNode *r);//递归实现中序遍历
    void PostOrder(TreeNode *r);//递归实现后续遍历
};
TreeNode* BinTree::CreateTree()//创建一棵二叉树
{
    TreeNode *p1=new TreeNode(1);
    TreeNode *p2=new TreeNode(2);
    TreeNode *p3=new TreeNode(3);
    TreeNode *p4=new TreeNode(4);
    TreeNode *p5=new TreeNode(5);
    TreeNode *p6=new TreeNode(6);
    TreeNode *p7=new TreeNode(7);
    TreeNode *p8=new TreeNode(8);
    TreeNode *p9=new TreeNode(9);
    p1->left=p2;
    p1->right=p3;
    p2->left=p4;
    p2->right=p5;
    p5->left=p6;
    p3->left=p7;
    p3->right=p8;
    p8->right=p9;
    root=p1;
    return root;
}


void Print(vector<int> &myarray)
{
    int num=myarray.size();
    for(int i=0; i<num;i++)
         cout<<myarray[i]<<"  ";
    cout<<endl;
    return;
}
vector<int> PrintFromTopToBottom(TreeNode* root)
{
        vector<int> res;
        if(root==NULL)
            return res;
        queue<TreeNode*> q;
        q.push(root);
        while(!q.empty())
            {
                res.push_back(q.front()->val);
                if(q.front()->left!=NULL)
                    q.push(q.front()->left);
                if(q.front()->right!=NULL)
                    q.push(q.front()->right);
                q.pop();
            }
            return res;
}

int main()
{

        BinTree t;
        TreeNode* root=t.CreateTree();//创建二叉树

       vector<int>vec= PrintFromTopToBottom( root );
        Print(vec);


        Mirror(root);
        vector<int>vec2= PrintFromTopToBottom( root );
        Print(vec2);
        return 0;
}