LeetCode - Flatten Binary Tree to Linked List
题意
把一个链表弄成一条链
思路
先序遍历一下，记录上一结点，把上一结点的left变为0，right变为当前结点。
代码
class Solution {
TreeNode *last;
public:
void DFS(TreeNode *root)
{
if (root != 0)
{
TreeNode *l = root->left;
TreeNode *r = root->right;
if (last == 0) last = root;
else
{
last->left = 0;
last->right = root;
last = root;
}
DFS(l);
DFS(r);
}
}
void flatten(TreeNode *root) {
last = 0;
DFS(root);
}
};