摘要：Given a singly linked list L: L0→L1→…→Ln-1→Ln,reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→… You must do this in-place without altering the nodes' values. For 阅读全文

摘要：Implement a basic calculator to evaluate a simple expression string. The expression string contains only non-negative integers, +, -, *, / operators a 阅读全文

摘要：题目： Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. The brackets must close in 阅读全文