Flatten Binary Tree to Linked List

Flatten a binary tree to a fake "linked list" in pre-order traversal.

Here we use the right pointer in TreeNode as the nextpointer in ListNode.

样例

              1               \     1          2    / \          \   2   5    =>    3  / \   \          \ 3   4   6          4                     \                      5                       \                        6

注意

Don't forget to mark the left child of each node to null. Or you will get Time Limit Exceeded or Memory Limit Exceeded.

class Solution {public:    void flatten(TreeNode *root) {        if(root==NULL) return;        if(root->left==NULL&&root->right==NULL) return;        if(root->left) flatten(root->left);        if(root->right) flatten(root->right);        TreeNode* tmp=root->left;        if(tmp==NULL) return;        while(tmp->right){            tmp=tmp->right;        }        tmp->right=root->right;        root->right=root->left;        root->left=NULL;    }};