摘要： 题目：Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.For example,"A man, a plan, a canal: Panama"is a palindrome."race a car"isnota palindrome.Note:Have you consider that the string might be empty? This is a good question 阅读全文

摘要： 题目：Given a linked list, swap every two adjacent nodes and return its head.For example,Given1->2->3->4, you should return the list as2->1->4->3.Your algorithm should use only constant space. You maynotmodify the values in the list, only nodes itself can be changed.解题思路：本题较简单，做3次指针变换 阅读全文

摘要： 题目：Given a linked list, remove thenthnode from the end of list and return its head.For example, Given linked list: 1->2->3->4->5, and n = 2. After removing the second node from the end, the linked list becomes 1->2->3->5.Note:Givennwill always be valid.Try to do this in one pass 阅读全文

摘要： 题目：You are climbing a stair case. It takesnsteps to reach to the top.Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?解题思路：这是一道斐波拉契数列题。看到斐波那契数列就自然想到利用递归，然而在这里递归的效率非常低，荣誉计算的数量增长的非常快，直接导致出现TLE（Time Limit Exceeded）错误。这是因为在递归的时候许多值被重复计算了多次，根据《C和指针》上对斐波那契数列的 阅读全文

摘要： 题目：Determine if a Sudoku is valid, according to:Sudoku Puzzles - The Rules.The Sudoku board could be partially filled, where empty cells are filled with the character'.'.A partially filled sudoku which is valid.Note:A valid Sudoku board (partially filled) is not necessarily solvable. Only th 阅读全文