摘要： Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists. 不申请新的节点（ 阅读全文

摘要： 20 Valid Parentheses Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. The bracke 阅读全文