Brush title 226. Invert Binary Tree

I, entitled Description

Topic 226. Invert Binary Tree, flip a binary tree. The difficulty is Easy!

Second, my answer

This topic, and traverse binary tree is similar. A recursive (before, during and after preorder, can be traversed by the layer):

class Solution{
	public:
		TreeNode* invertTree(TreeNode* root){
			if(root ==NULL) return root;
			TreeNode * p = root->left;
			root->left = root->right;
			root->right = p;
			root->left = invertTree(root->left);
			root->right = invertTree(root->right);
			return root;
		}
};

Properties are as follows:

Runtime: 4 ms, faster than 65.13% of C++ online submissions for Invert Binary Tree.
Memory Usage: 10 MB, less than 5.45% of C++ online submissions for Invert Binary Tree.

Third, the optimization measures

Non-recursive algorithm, implemented in breadth-first traversal of the following:

class Solution{
	public:
		//non-recursive using level
		TreeNode* invertTree(TreeNode* root){
			if(root == NULL) return root;
			queue<TreeNode*> q;
			TreeNode* tmp,*cur;
			q.push(root);
			while(! q.empty()){
				cur = q.front();
				q.pop();
				tmp = cur->left;
				cur->left = cur->right;
				cur->right = tmp;
				if(cur->left !=NULL ){
					q.push(cur->left);
				}
				if(cur->right != NULL){
					q.push(cur->right);
				}
			}
			
			return root;
		}
};

Properties are as follows:

Runtime: 0 ms, faster than 100.00% of C++ online submissions for Invert Binary Tree.
Memory Usage: 10.2 MB, less than 5.45% of C++ online submissions for Invert Binary Tree.