摘要：
Implement atoi to convert a string to an integer. Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below 阅读全文
摘要：
比较两个字符串A和B，确定A中是否包含B中所有的字符。字符串A和B中的字符都是 大写字母 注意事项 在 A 中出现的 B 字符串里的字符不需要连续或者有序。 样例 给出 A = "ABCD" B = "ACD"，返回 true 给出 A = "ABCD" B = "AABC"， 返回 false 思 阅读全文
摘要：
Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. The brackets must close in the 阅读全文
摘要：
We define the Perfect Number is a positive integer that is equal to the sum of all its positive divisors except itself. Now, given an integer n, write 阅读全文