CODEWITHSUNDEEP
cloopsdice
user1695758
user1695758

Reputation: 173

Trouble with Die Roll Program

I wrote this program that rolls a pair of dice 20000 times. The rules are:

Second roll rules:

At the end it calculates a percentage of games won. My problem is that I should be getting a percentage of games won around 39%-60% according to a colleagues, but every time I run the program, I get around 20% and I don't understand why. Am I doing something wrong? Can someone help me please?

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

main()
{   
int dieOne, dieTwo, keyValue, value, wins = 0, firstWins = 0, subWins = 0, loss = 0, count=0;
double percentWin, percentFirstWins, percentSubWins;
srand(time(NULL));

do{
dieOne = rand() % 6 + 1;
dieTwo = rand() % 6 + 1;
value = dieOne + dieTwo;
count++;


if (value==7||value==11) {
    firstWins++;
    wins++;
}

else if (value== 2||value==3||value==12) {
    loss++;
}

else {
    do{ 
    keyValue = value;

    dieOne = rand() % 6 + 1;
    dieTwo = rand() % 6 + 1;
    value = dieOne + dieTwo;
    count++;

    if (value==7) {
    subWins++;
    wins++;
    }

    else if (value = keyValue) { 
        loss++;
    }

    } while ( value != 7 && value != keyValue );
}
} while (count <= 20000);

    percentWin = (double) wins/count * 100;
    percentFirstWins = (double) firstWins/count * 100;
    percentSubWins = (double) subWins/count * 100;
    printf("You won %.1lf percent of your games! \nYou won %.1lf percent of games on the first roll.\nYou won %.1lf percent of games on the second roll.\n", percentWin, percentFirstWins, percentSubWins );

    system("pause");
}

There are 6 possible ways to roll a 7 and two possible ways to roll an 11.
That's a total of 8 possible ways to win on the first roll.
There are 36 (6^2) possible ways to roll the dice. This means you have an 8 in 36 chance to win on the first roll or around 22% of the time.

Moreover, we have 2 possible ways to roll a 2, and 2 possible ways to roll a 3, and 2 possible ways to roll a 12. So that means there is a 1 in 6 chance (6/36) of losing on the first roll, or about 17% of the time.

So the remaining 61% of wins and losses have to come from the second roll. Whatever the case, my program is generating a very high losing streak, whereas the programs of my colleagues seem to generate a 40-60 percent of total wins. Where am I going wrong?

Upvotes: 1

Views: 316

Answers (1)

Cody
Cody

Reputation: 2482

This may be what's causing your problem:

else if (value = keyValue) {

You're assigning, rather than comparing. This will always evaluate to true, thus artificially inflating your losses. You should be using == here instead of =.

Also, for rolls that are neither a win nor a loss, you're not incrementing either the wins or the loss counter for either of those, but you are adding to count. So you're going to end up with a situation where wins + loss != count. When you calculate the win percentage, try calculating it as wins / (loss + wins).

Upvotes: 1

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