LeetCode 63. Unique Paths II 不同路径 II A robot is located at the top-left corner of a m x n grid. The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid. Now consider if some obstacles are added to the grids. How many unique paths would there be?

LeetCode 62. Unique Paths 不同路径 A robot is located at the top-left corner of a m x n grid. The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid. How many possible unique paths are there?

LeetCode 287. Find the Duplicate Number 寻找重复数 Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. Assume that there is only one duplicate number, find the duplicate one.

LeetCode 142. Linked List Cycle II 环形链表 II Given a linked list, return the node where the cycle begins. If there is no cycle, return null.

LeetCode 86. Partition List 分隔链表 Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x. You should preserve the original relative order of the nodes in each of the two partitions.

LeetCode 61. Rotate List 旋转链表 Given a linked list, rotate the list to the right by k places, where k is non-negative.

LeetCode 143. Reorder List 重排链表 Given a singly linked list L: L0→L1→…→Ln-1→Ln, reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→… You may not modify the values in the list's nodes, only nodes itself may be changed.