摘要：
Valid operators are +, -, *, /. Each operand may be an integer or another expression. Some examples: ["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9 ["4", "13", "5", "/", "+"] -> (4 + (13 / 5 阅读全文
摘要：
Given an input string, reverse the string word by word. For example, Given s = "the sky is blue", return "blue is sky the". Clarification: What constitutes a word? A sequence of non-spa... 阅读全文