一朵云

题目 Given a string, find the first non-repeating character in it and return it’s index. If it doesn’t exist, return -1. Note: You may assume the string contain only lowercase letters. 思路1 可以建立一个哈希表，

题目 Say you have an array for which the ith element is the price of a given stock on day i. Design an algorithm to find the maximum profit. You may complete as many transactions as you like (ie, buy o