摘要：
**Example 1:** ``` Input: nums = [1,1,2] Output: 2, nums = [1,2,_] Explanation: Your function should return k = 2, with the first two elements of nums 阅读全文
摘要：
Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: 阅读全文
摘要：
Write a function to find the longest common prefix string amongst an array of strings. If there is no common prefix, return an empty string ```""```. 阅读全文