例子: ["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9
["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6例子: ["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -例子: ["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9
["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6例子: ["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -