Evaluate Reverse Polish Notation

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Adobe interview context: Evaluate Reverse Polish Notation is a Medium Stack problem — Monotonic stack or bracket matching — watch for O(n) single-pass solutions.

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Pattern: Stack

Read from stdin, write to stdout. Classic interview problem #150.

Problem

Evaluate Reverse Polish Notation — Adobe interview prep · Stack

Classic interview problem #150.

Input (stdin)

Line 1: RPN tokens space-separated

Output (stdout)

Evaluated integer

Your program must read from stdin and write the answer to stdout (no extra debug text).

Examples

Sample

Input

2 1 + 3 *

Output

Hints

Input format: Line 1: RPN tokens space-separated
DSA Interview 150 — Stack
Problem #150
Frequently asked at Adobe
Stack

Your solution

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class Program
{
    static int[] Ria(string line = null)
    {
        line ??= Console.ReadLine();
        if (string.IsNullOrWhiteSpace(line)) return Array.Empty<int>();
        return line.Trim().Split(new[] { ' ', ',', '\t' }, StringSplitOptions.RemoveEmptyEntries)
            .Select(int.Parse).ToArray();
    }
    static string[] Rsa()
    {
        int n = int.Parse(Console.ReadLine());
        var arr = new string[n];
        for (int i = 0; i < n; i++) arr[i] = Console.ReadLine();
        return arr;
    }
    static void W(params object[] parts) => Console.WriteLine(string.Join(" ", parts));
    static void Wb(bool v) => Console.WriteLine(v ? "true" : "false");
    static void Wi(int v) => Console.WriteLine(v);
    static void Ws(string v) => Console.WriteLine(v);

static void Main()
    {
        // Read from stdin (see problem statement for format)
        // Line 1: RPN tokens space-separated

}
}

Ready — edit the code above and click Run or Submit.

Solution

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class Program
{
    static int[] Ria(string line = null)
    {
        line ??= Console.ReadLine();
        if (string.IsNullOrWhiteSpace(line)) return Array.Empty<int>();
        return line.Trim().Split(new[] { ' ', ',', '\t' }, StringSplitOptions.RemoveEmptyEntries)
            .Select(int.Parse).ToArray();
    }
    static string[] Rsa()
    {
        int n = int.Parse(Console.ReadLine());
        var arr = new string[n];
        for (int i = 0; i < n; i++) arr[i] = Console.ReadLine();
        return arr;
    }
    static void W(params object[] parts) => Console.WriteLine(string.Join(" ", parts));
    static void Wb(bool v) => Console.WriteLine(v ? "true" : "false");
    static void Wi(int v) => Console.WriteLine(v);
    static void Ws(string v) => Console.WriteLine(v);

    static void Main()
    {
var tokens = Console.ReadLine().Split(' ', StringSplitOptions.RemoveEmptyEntries);
var st = new Stack<int>();
foreach (var t in tokens) {
    if (t == "+" || t == "-" || t == "*" || t == "/") {
        int b = st.Pop(), a = st.Pop();
        int r = t switch { "+" => a + b, "-" => a - b, "*" => a * b, _ => a / b };
        st.Push(r);
    } else st.Push(int.Parse(t));
}
Wi(st.Peek());
    }
}

Try solving on your own first, then reveal the official answer.

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Problem

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