CODEWITHSUNDEEP
c++c++11while-loopdo-while
Minjae
Minjae

Reputation: 31

C++ do while not looping

I understand I can just use for-loop to define prime number, but before I implement for loop into that topic, I had a thought that I maybe could make one with while loop or do-while. Somehow, my do-while loop seems not to be working correctly.

My theory was that I could find prime number for checking the remainder of divisor where divisor keeps decreasing by 1 until divisor reaches 1. (Although 'until divisor reaches 1.' part is not in the code, I would assumed remainder of 0 would appear anyway before divisor goes below 0.)

However, it keeps halting before remainder reaches 0. What did I do wrong? I've even tried both instead of (remainder<1 && remainder!=1)below but still no luck.

while (remainder<1)
 while (remainder==1)

#include <iostream>
using namespace std;
int main()
{
    int number, divisor, remainder;
    cin >> number;
    divisor=number-1;
    cout << "You've put " << number << ".\n";
    do {
      divisor = divisor - 1;
      remainder=number%divisor;
    }
    while (remainder<1 && remainder!=1);
    cout << divisor << "  "  << remainder << "  " << number << "  "  << "Divisor, remainder, number\n";
    return 0;
}

Upvotes: 0

Views: 1040

Answers (1)

Barmar
Barmar

Reputation: 780655

First, you have a typo in your variable assignment. This line:

number = divisor - 1;

should be:

divisor = number - 1;

The while() condition should be while (remainder != 0), so that the loop keeps repeating as long as you haven't found a divisor. If you want to be more explicit, you could use while (divisor > 1 && remainder != 0). There's no need to repeat when divisor == 1 because that's a divisor of all integers.

Upvotes: 3

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