How to resolve the algorithm Two bullet roulette step by step in the C programming language

Published on 7 June 2024 03:52 AM
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How to resolve the algorithm Two bullet roulette step by step in the C programming language

Table of Contents

Problem Statement

The following is supposedly a question given to mathematics graduates seeking jobs on Wall Street:

Youtube video on the Russian 1895 Nagant revolver [[1]]

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Two bullet roulette step by step in the C programming language

The provided code is a C program that simulates a Russian roulette game. The game takes a sequence of actions as input ("L", "S", "F"), and the program calculates the probability of death.

  • Global Variables:

    • nextInt(int size): Used to generate a random integer within the specified size.
    • cylinder[6]: A boolean array representing the six chambers of the revolver, where true indicates a loaded chamber.
  • Functions:

    • rshift(): Rotates the revolver cylinder by shifting the chambers to the right.
    • unload(): Unloads the revolver by setting all chambers to false.
    • load(): Loads the revolver by setting the first chamber to true and rotating the cylinder.
    • spin(): Spins the revolver cylinder by a random number of positions (1-6).
    • fire(): Fires the revolver by checking if the first chamber is loaded and rotating it. It returns true if the shot is successful.
    • method(const char *s): This is the main game simulation method. It takes a string s of actions ("L", "S", "F") and performs the corresponding actions on the revolver. It returns 1 if the player dies (shot successfully), and 0 otherwise.
    • append(char *out, const char *txt): Appends the specified text txt to the output string out with a comma separator if out is not empty.
    • mstring(const char *s, char *out): Converts the input string s of actions ("L", "S", "F") into a descriptive string (e.g., "load", "spin", "fire") and appends it to the output string out.
    • test(char *src): This function runs a test with a given input string src. It simulates the game tests times and calculates the probability of death for the given sequence of actions. The test results are printed with the corresponding descriptive string.
  • Main Function:

    • Seeds the random number generator using the current time.
    • Runs tests for four different input strings:
      • LSLSFSF
      • LSLSFF
      • LLSFSF
      • LLSFF
    • For each test, it calculates the probability of death and prints the results.

Source code in the c programming language

#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

static int nextInt(int size) {
    return rand() % size;
}

static bool cylinder[6];

static void rshift() {
    bool t = cylinder[5];
    int i;
    for (i = 4; i >= 0; i--) {
        cylinder[i + 1] = cylinder[i];
    }
    cylinder[0] = t;
}

static void unload() {
    int i;
    for (i = 0; i < 6; i++) {
        cylinder[i] = false;
    }
}

static void load() {
    while (cylinder[0]) {
        rshift();
    }
    cylinder[0] = true;
    rshift();
}

static void spin() {
    int lim = nextInt(6) + 1;
    int i;
    for (i = 1; i < lim; i++) {
        rshift();
    }
}

static bool fire() {
    bool shot = cylinder[0];
    rshift();
    return shot;
}

static int method(const char *s) {
    unload();
    for (; *s != '\0'; s++) {
        switch (*s) {
        case 'L':
            load();
            break;
        case 'S':
            spin();
            break;
        case 'F':
            if (fire()) {
                return 1;
            }
            break;
        }
    }
    return 0;
}

static void append(char *out, const char *txt) {
    if (*out != '\0') {
        strcat(out, ", ");
    }
    strcat(out, txt);
}

static void mstring(const char *s, char *out) {
    for (; *s != '\0'; s++) {
        switch (*s) {
        case 'L':
            append(out, "load");
            break;
        case 'S':
            append(out, "spin");
            break;
        case 'F':
            append(out, "fire");
            break;
        }
    }
}

static void test(char *src) {
    char buffer[41] = "";
    const int tests = 100000;
    int sum = 0;
    int t;
    double pc;

    for (t = 0; t < tests; t++) {
        sum += method(src);
    }

    mstring(src, buffer);
    pc = 100.0 * sum / tests;

    printf("%-40s produces %6.3f%% deaths.\n", buffer, pc);
}

int main() {
    srand(time(0));

    test("LSLSFSF");
    test("LSLSFF");
    test("LLSFSF");
    test("LLSFF");

    return 0;
}


  

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