Re: [閒聊] 每日LeetCode

[SecondRun (南爹摳打)]

150.Evaluate Reverse Polish Notation

直接看example

Input: tokens = ["2","1","+","3","*"]
Output: 9
Explanation: ((2 + 1) * 3) = 9

C# code:
https://i.imgur.com/XNoiGMm.png
public class Solution
{
        public int EvalRPN(string[] tokens)
        {
                Stack<int> stack = new Stack<int>();
                int a, b;
                foreach (string token in tokens)
                {
                        if (int.TryParse(token, out int value))
                        {
                                stack.Push(value);
                                continue;
                        }
                        b = stack.Pop();
                        a = stack.Pop();
                        stack.Push(Calculate(a, b, token));
                }
                return stack.Pop();
        }

        public int Calculate(int a, int b, string op)
        {
                switch (op)
                {
                        case "+":
                                return a + b;
                        case "-":
                                return a - b;
                        case "*":
                                return a * b;
                        case "/":
                                return a / b;
                }
                return -1;
        }
}

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https://i.imgur.com/63x4HSh.jpg

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