Merge two sorted linked lists and return it as a new sorted list.
The new list should be made by splicing together the nodes of the first two lists.
* Given a string s containing just the characters '(', ')', '{', '}', '[', ']', determine if the input string is valid.
* An input string is valid if:
* 1. Open brackets must be closed by the same type of brackets.
* 2. Open brackets must be closed in the correct order.
Given an array nums of n integers, are there elements a,b,c in nums such that a+b+c = 0?
Find all unique triplets in the array which gives the sum of zero.
Note : 過不了 TimeLimit 還需要修改
Write a function to find the longest common prefix string amomgst an array of strings.
If there is no common prefix, return an empty string "".
Roman numerals are represented by seven different symbols: I, V, X, L, C, D, M.
Roman numerals are represented by seven different symbols: I, V, X, L, C, D, M
Detemine whether an integer is palindrome. An integer is a palindrome when it reads the same backward as forward.
Detemine whether an integer is palindrome. An integer is a palindrome when it reads the same backward as forward.
Implement atoi which converts a string to integer
Given a 32-bit signed integer, reverse digits of an integer
Given a string s, find the longest palindromic substring in s, you may assume that the maximun length of s is 1000.
Given two sorted arrays nums1 and nums2 of size m and n respectively,
return the median of the two sorted arrays.
Given a string s, find the length of the longest substring without repeating characters.