leetcode226:反转二叉树

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