Given a singly linked list, determine if it is a palindrome. Follow up:Could you do it in O(n) time and O(1) space? Subscribe to see which companies asked this question   思路: 1.利用快慢两个指针找到中间结点 2.从中间结点下一个结点开始逆置链表,得到新的链表 3.新的链表与原来链表依次比较结点,如有不同,return fa…

Given a binary tree, flatten it to a linked list in-place. For example,Given 1 / \ 2 5 / \ \ 3 4 6 The flattened tree should look like: 1 \ 2 \ 3 \ 4 \ 5 \ 6 click to show hints. Hints: If you notice carefully in the flattened tree, each node's right…

114. Flatten Binary Tree to Linked List (Medium) 453. Flatten Binary Tree to Linked List (Easy) 解法1: 用stack. class Solution { public: void flatten(TreeNode *root) { if(!root) return; TreeNode *pnode = NULL; stack<TreeNode*> s; s.push(root); while(!s…

Given a binary tree, flatten it to a linked list in-place. For example,Given 1 / \ 2 5 / \ \ 3 4 6 The flattened tree should look like: 1 \ 2 \ 3 \ 4 \ 5 \ 6 题目大意:给一个二叉树,将它转为一个list,转换后的序列应该是先序遍历,list由这棵树的右孩子表示. 解题思路:递归的处理左子树,然后处理右子树,将左孩子的右孩子置为当前节点的右孩…

138. Copy List with Random Pointer //不从head走 前面加一个dummy node 从dummy走先连head 只需记录当前节点 //这样就不需要考虑是先new node还是先找联系 //扫两遍 先建立节点和next 利用map<node*, node*>old2new 来找random linked list 一般用while循环来建立loop 147. Insertion Sort List //这里dummy是新插入的sorted list的头,所有…

Write a function to delete a node (except the tail) in a singly linked list, given only access to that node. Supposed the linked list is 1 -> 2 -> 3 -> 4 and you are given the third node with value 3, the linked list should become 1 -> 2 ->…

题目: Given a binary tree, flatten it to a linked list in-place. For example, Given 1 / \ 2 5 / \ \ 3 4 6 The flattened tree should look like: 1 \ 2 \ 3 \ 4 \ 5 \ 6 题解:如hint所给出,这道题就是使用先序遍历,遍历到的值作为新的右孩子存起来,左孩子变为空.注意的是,因为右孩子会更新,所以为了递归右子树,要在更新之前提前保存右孩子.整个…

Given a non-negative number represented as a singly linked list of digits, plus one to the number. The digits are stored such that the most significant digit is at the head of the list. Example: Input: ->-> Output: ->-> 思路:递归. /** * Definition…

Question 876. Middle of the Linked List Solution 题目大意:求链表的中间节点 思路:构造两个节点,遍历链接,一个每次走一步,另一个每次走两步,一个遍历完链表,另一个恰好在中间 Java实现: public ListNode middleNode(ListNode head) { ListNode slow = head; ListNode fast = head; while (fast != null) { fast = fast.next; i…

Question 206. Reverse Linked List Solution 题目大意:对一个链表进行反转 思路: Java实现: public ListNode reverseList(ListNode head) { ListNode newHead = null; while (head != null) { ListNode tmp = head.next; head.next = newHead; newHead = head; head = tmp; } return new…