LiBK-铁甲依然在

问题描述

Given the root of a binary tree, return the level order traversal of its nodes’ values. (i.e., from left to right, level by level).

Example :

1
2

Input: root = [3,9,20,null,null,15,7]
Output: [[3],[9,20],[15,7]]

问题描述

Given the root of a binary tree, return the inorder traversal of its nodes’ values.

Constraints:

• The number of nodes in the tree is in the range [0, 100].
• -100 <= Node.val <= 100

问题描述

Given the root of a binary tree, return the postorder traversal of its nodes’ values.

Constraints:

• The number of the nodes in the tree is in the range [0, 100].
• -100 <= Node.val <= 100

问题描述

Given the root of a binary tree, return the preorder traversal of its nodes’ values.

Constraints:

• The number of nodes in the tree is in the range [0, 100].
• -100 <= Node.val <= 100

问题描述

You are given the head of a singly linked-list. The list can be represented as:

1

L0 → L1 → … → Ln - 1 → Ln

Reorder the list to be on the following form:

1

L0 → Ln → L1 → Ln - 1 → L2 → Ln - 2 → …

You may not modify the values in the list’s nodes. Only nodes themselves may be changed.

Example :

1
2

Input: head = [1,2,3,4,5]
Output: [1,5,2,4,3]

Constraints:

• The number of nodes in the list is in the range [1, 5 * 104].
• 1 <= Node.val <= 1000

问题描述

Given the head of a linked list, return the list after sorting it in ascending order.

Constraints:

• The number of nodes in the list is in the range [0, 5 * 104].
• -105 <= Node.val <= 105

问题描述

Given the head of a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list. Return the linked list sorted as well.

Example :

1
2

Input: head = [1,2,3,3,4,4,5]
Output: [1,2,5]

Constraints:

• The number of nodes in the list is in the range [0, 300].
• -100 <= Node.val <= 100
• The list is guaranteed to be sorted in ascending order.

问题描述

Given the head of a sorted linked list, delete all duplicates such that each element appears only once. Return the linked list sorted as well.

Constraints:

• The number of nodes in the list is in the range [0, 300].
• -100 <= Node.val <= 100
• The list is guaranteed to be sorted in ascending order.

问题描述

Given the head of a singly linked list, group all the nodes with odd indices together followed by the nodes with even indices, and return the reordered list.

The first node is considered odd, and the second node is even, and so on.

Note that the relative order inside both the even and odd groups should remain as it was in the input.

You must solve the problem in O(1) extra space complexity and O(n) time complexity.

Example :

1
2

Input: head = [2,1,3,5,6,4,7]
Output: [2,3,6,7,1,5,4]

Constraints:

• n == number of nodes in the linked list
• 0 <= n <= 104
• -106 <= Node.val <= 106

问题描述

Given the head of a singly linked list, return true if it is a palindrome.

Constraints:

• The number of nodes in the list is in the range [1, 105].
• 0 <= Node.val <= 9

Follow up: Could you do it in O(n) time and O(1) space?