CODEWITHSUNDEEP
c++
Bogdan
Bogdan

Reputation: 11

Console has input prompt then closes without output on a very simple program

I have a very simple program that won't give any console output.

I've tried getting input at the end using cin.get() and holding with system("pause"). I've also tried getting input at the start of the program then outputting at the end.

#include <iostream>
using namespace std;

int main(){
    int bulb, bulbOpen=0, multiple;

    for ( bulb=1; bulb<101 ; bulb=bulb+1 ){
        for ( multiple=1; 100; multiple++){
            if (bulb/multiple==0){
                bulb = bulb * (-1);
            }
        }
        if ( bulb<<0 ){
            bulbOpen = bulbOpen + 1;
        }
    }

    cout << "The remaining open light bulbs are " << bulbOpen << "." << endl;

    return 0;
}

I'm a beginner programmer so any help, recommendations and explanations are very welcome.

EDIT:

Thanks to Rapha for the fixes and the advice, here's the updated code:

#include <iostream>

int main(){
    int bulb, bulbCopy, bulbOpen=0, multiple;

    for ( bulb=1; bulb<101 ; bulb++ ){
        bulbCopy = bulb;
         for ( multiple=1; multiple<101; multiple++){
            
            if (bulbCopy%multiple==0){
                bulbCopy = bulbCopy * (-1);
            }
        }
        if ( bulbCopy<0 ){
            bulbOpen = bulbOpen + 1;
        }
    }

    std::cout << "The remaining open light bulbs are " << bulbOpen << "." << std::endl;

    std::cin.get();
    return 0;
}

The exercise went like this: You've got 100 light bulbs. You take every number from 1-100 and for every lightbulb with the position a multiple of said number, you switch it's current state. So basically if you've got bulb 2, you first switch it ON because it's a multiple of 1, then you switch it OFF because it's a multiple of 2. And you've got to check how many remaining lightbulbs are still open by the end.

The answer is 10.

Upvotes: 0

Views: 50

Answers (1)

Endunry
Endunry

Reputation: 974

The Main-Problem why you get no output is, that the code is causing an infinity-loop (The loop cant escape and will run forever) and you never reach the std::cout part of the code

Ok there's a lot going on and the first thing is (You probably will hear this a lot on this platform) don't use using namespace std; instead use the std::-prefix for c++-Standard Things. I think its ok to use if you start out, but its a really bad Practice.

Then another thing is, cin.get() already 'pauses' or interrupting the program until you entered an input so system("pause") really isn't needed here.

To get input simply do it like that:

int input;
std::cin >> input;
std::cout << "My output was: " << input;

Then another thing is, i dont really know what you try to do with the nested for-loops but in the second for-loop you have a conditions that doesnt really make sense

for(multiple=1; 100; multiple++)
                ^^^

What you probably want is something like

for(multiple=1; multiple<100; multiple++)

And then saying bulb/multiple==0 doesn't really make sense either, because its only true if bulb is 0, maybe you mean bulb%multiple==0 (modulo).

And there's probably a typo in one condition where you wrote bulb<<0 where you probably want to write bulb<0

But no matter what you do, it still runs into a infinite loop, because the conditions are weird. And in normal cases you really shouldn't change the iteration-variable of your loop inside your loop (only if you know thats exactly what you want) but in most cases that just breaks your program, especially if youre starting to learn the language.

Maybe if you say exactly what you want, we can help you more.

Upvotes: 2

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