[226] Invert Binary Tree

Invert a binary tree.

Example:

Input:

     4
   /   \
  2     7
 / \   / \
1   3 6   9

Output:

     4
   /   \
  7     2
 / \   / \
9   6 3   1

翻转一棵二叉树。EZ题。
方法1：整体思路就是层次遍历，然后把左右孩子对调。

class Solution {
public:
    TreeNode* invertTree(TreeNode* root) 
    {
        queue<TreeNode*> q;
        if(root!=nullptr)
        {
            q.push(root);
            while(!q.empty())
            {
               TreeNode* node = q.front();
                q.pop();
               swapChild(node);
               if(node->left!=nullptr)
                   q.push(node->left);
                if(node->right!=nullptr)
                    q.push(node->right);
            }
        }
        return root;
    }
    void swapChild(TreeNode* node)
    {
        if(node != nullptr)
        {
            TreeNode* temp = node->right;
            node->right = node->left;
            node->left = temp;
        }
    }
};

方法2：递归求解，简洁的让人觉得可怕,跑的还飞快，推荐食用👍

class Solution {
public:
    TreeNode* invertTree(TreeNode* root) 
    {
        if(root!=nullptr)
        {
            
            auto temp = root->right;
            root->right = invertTree(root->left);
            root->left = invertTree(temp);
        }
        return root;
    }
};