[剑指Offer] 18.二叉树的镜像

题目描述

操作给定的二叉树，将其变换为源二叉树的镜像。

输入描述:

    	    8
    	   /  \
    	  6   10
    	 / \  / \
    	5  7 9 11
    	镜像二叉树
    	    8
    	   /  \
    	  10   6
    	 / \  / \
    	11 9 7  5

【思路1】递归，左右孩子交换再分别递归左右子树

 /*
 struct TreeNode {
     int val;
     struct TreeNode *left;
     struct TreeNode *right;
     TreeNode(int x) :
             val(x), left(NULL), right(NULL) {
     }
 };*/
 class Solution {
 public:
     void Mirror(TreeNode *pRoot) {
         if(pRoot == NULL)
             return ;
         TreeNode *temp = pRoot->left;
         pRoot->left = pRoot->right;
         pRoot->right = temp;
         Mirror(pRoot->left);
         Mirror(pRoot->right);
     }
 };

【思路2】非递归，栈实现

 /*
 struct TreeNode {
     int val;
     struct TreeNode *left;
     struct TreeNode *right;
     TreeNode(int x) :
             val(x), left(NULL), right(NULL) {
     }
 };*/
 class Solution {
 public:
     void Mirror(TreeNode *pRoot) {
         if(pRoot == NULL)
             return ;
         stack<TreeNode*> StackNode;
         StackNode.push(pRoot);
         while(!StackNode.empty()){
             TreeNode* tree = StackNode.top();
             StackNode.pop();
             if(tree->left || tree->right){
                 TreeNode* temp = tree->left;
                 tree->left = tree->right;
                 tree->right = temp;
             }
             if(tree->left)
                 StackNode.push(tree->left);
             if(tree->right)
                 StackNode.push(tree->right);
         }
     }
 };