226. 翻转二叉树

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def invertTree(self, root: TreeNode) -> TreeNode:
        if not root:
            return None
        stack =[root]
        while stack:
            node=stack.pop(0)
            node.left,node.right=node.right,node.left
            if node.left:
                stack.append(node.left)
            if node.right:
                stack.append(node.right)
        return root

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        if(root==NULL)return root;
        auto q=queue<TreeNode*>();
        q.push(root);
        while(!q.empty()){
            auto n=q.front();q.pop();
            swap(n->left,n->right);
            if(n->left!=nullptr){
                q.push(n->left);
            }
            if(n->right!=nullptr){
                q.push(n->right);
            }
        }
        return root;
    }
};