Task: 24 game




Go: package main

import (
    "fmt"
    "math"
    "math/rand"
    "time"
)

func main() {
    rand.Seed(time.Now().Unix())
    n := make([]rune, 4)
    for i := range n {
        n[i] = rune(rand.Intn(9) + '1')
    }
    fmt.Printf("Your numbers: %c\n", n)
    fmt.Print("Enter RPN: ")
    var expr string
    fmt.Scan(&expr)
    if len(expr) != 7 {
        fmt.Println("invalid. expression length must be 7." +
            " (4 numbers, 3 operators, no spaces)")
        return
    }
    stack := make([]float64, 0, 4)
    for _, r := range expr {
        if r >= '0' && r <= '9' {
            if len(n) == 0 {
                fmt.Println("too many numbers.")
                return
            }
            i := 0
            for n[i] != r {
                i++
                if i == len(n) {
                    fmt.Println("wrong numbers.")
                    return
                }
            }
            n = append(n[:i], n[i+1:]...)
            stack = append(stack, float64(r-'0'))
            continue
        }
        if len(stack) < 2 {
            fmt.Println("invalid expression syntax.")
            return
        }
        switch r {
        case '+':
            stack[len(stack)-2] += stack[len(stack)-1]
        case '-':
            stack[len(stack)-2] -= stack[len(stack)-1]
        case '*':
            stack[len(stack)-2] *= stack[len(stack)-1]
        case '/':
            stack[len(stack)-2] /= stack[len(stack)-1]
        default:
            fmt.Printf("%c invalid.\n", r)
            return
        }
        stack = stack[:len(stack)-1]
    }
    if math.Abs(stack[0]-24) > 1e-6 {
        fmt.Println("incorrect.", stack[0], "!= 24")
    } else {
        fmt.Println("correct.")
    }
}


Java: import java.util.*;

public class Game24 {
    static Random r = new Random();

    public static void main(String[] args) {

        int[] digits = randomDigits();
        Scanner in = new Scanner(System.in);

        System.out.print("Make 24 using these digits: ");
        System.out.println(Arrays.toString(digits));
        System.out.print("> ");

        Stack<Float> s = new Stack<>();
        long total = 0;
        for (char c : in.nextLine().toCharArray()) {
            if ('0' <= c && c <= '9') {
                int d = c - '0';
                total += (1 << (d * 5));
                s.push((float) d);
            } else if ("+/-*".indexOf(c) != -1) {
                s.push(applyOperator(s.pop(), s.pop(), c));
            }
        }
        if (tallyDigits(digits) != total)
            System.out.print("Not the same digits. ");
        else if (Math.abs(24 - s.peek()) < 0.001F)
            System.out.println("Correct!");
        else
            System.out.print("Not correct.");
    }

    static float applyOperator(float a, float b, char c) {
        switch (c) {
            case '+':
                return a + b;
            case '-':
                return b - a;
            case '*':
                return a * b;
            case '/':
                return b / a;
            default:
                return Float.NaN;
        }
    }

    static long tallyDigits(int[] a) {
        long total = 0;
        for (int i = 0; i < 4; i++)
            total += (1 << (a[i] * 5));
        return total;
    }

    static int[] randomDigits() {        
        int[] result = new int[4];
        for (int i = 0; i < 4; i++)
            result[i] = r.nextInt(9) + 1;
        return result;
    }
}