摘要：
Description: Count the number of prime numbers less than a non-negative number, n. 题解：就是线性筛素数的模板题。 阅读全文
摘要：
Given a range [m, n] where 0 <= m <= n <= 2147483647, return the bitwise AND of all numbers in this range, inclusive. For example, given the range [5, 阅读全文
摘要：
Remove all elements from a linked list of integers that have value val. ExampleGiven: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6Return: 1 --> 2 -- 阅读全文
摘要：
题意：把一个链表倒过来。 题解：有递归和非递归两种方式，主要就是考察指针操作的熟悉程度。 递归的方法： 非递归：就一个一个转过来方向就好了。转的时候需要用两个辅助指针，一个指向该节点的前一个节点，一个指向后一个节点。 阅读全文
摘要：
Given two strings s and t, determine if they are isomorphic. Two strings are isomorphic if the characters in s can be replaced to get t. All occurrenc 阅读全文
摘要：
Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacen 阅读全文
摘要：
Write an algorithm to determine if a number is "happy". A happy number is a number defined by the following process: Starting with any positive intege 阅读全文