Console Application is not running and shows nothing












-1















The problem is to solve this.



The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?



I wrote this code



#include <iostream>
#include <math.h>
using namespace std;

bool prime(long int a);

int main()
{
long int b = 600851475143/2;
long int k;



for(long int i = 1; i <= b ; i++)
{
if(b % i == 0 && prime(i) == true)
{
k = i;
}
}
cout << k << endl;
return 0;



}

bool prime(long int a)
{
bool p = true;

for(long int i = 2; i <= sqrt(a) && p == true ; i++)
if(a % i == 0) p = false;

return p;
}


and when I execute after a build, it opens a console , and shows nothing










share|improve this question























  • Debuggers are a brilliant tool for solving problems like this. Pop a breakpoint at the start of the program, start up the program, and start start stepping until the program blocks or starts going around in circles.

    – user4581301
    Nov 25 '18 at 21:36











  • g++ spits out warning: overflow in implicit constant conversion [-Woverflow] long int b = 600851475143/2; You should resolve this. Come to think of it, 600851475143/2; is a darn big number. You might want to reconsider using it as a loop bound.

    – user4581301
    Nov 25 '18 at 21:42











  • Regarding the prime computation, this is a brutally slow way to do this. Consider the number of times you are recomputing the i = 2 case.

    – user4581301
    Nov 25 '18 at 21:45











  • I didn't complete the previous thought. Use memoization to reduce the amount of redundant work you have to do. See if you can take advantage of a Prime Number Sieve.

    – user4581301
    Nov 25 '18 at 22:01
















-1















The problem is to solve this.



The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?



I wrote this code



#include <iostream>
#include <math.h>
using namespace std;

bool prime(long int a);

int main()
{
long int b = 600851475143/2;
long int k;



for(long int i = 1; i <= b ; i++)
{
if(b % i == 0 && prime(i) == true)
{
k = i;
}
}
cout << k << endl;
return 0;



}

bool prime(long int a)
{
bool p = true;

for(long int i = 2; i <= sqrt(a) && p == true ; i++)
if(a % i == 0) p = false;

return p;
}


and when I execute after a build, it opens a console , and shows nothing










share|improve this question























  • Debuggers are a brilliant tool for solving problems like this. Pop a breakpoint at the start of the program, start up the program, and start start stepping until the program blocks or starts going around in circles.

    – user4581301
    Nov 25 '18 at 21:36











  • g++ spits out warning: overflow in implicit constant conversion [-Woverflow] long int b = 600851475143/2; You should resolve this. Come to think of it, 600851475143/2; is a darn big number. You might want to reconsider using it as a loop bound.

    – user4581301
    Nov 25 '18 at 21:42











  • Regarding the prime computation, this is a brutally slow way to do this. Consider the number of times you are recomputing the i = 2 case.

    – user4581301
    Nov 25 '18 at 21:45











  • I didn't complete the previous thought. Use memoization to reduce the amount of redundant work you have to do. See if you can take advantage of a Prime Number Sieve.

    – user4581301
    Nov 25 '18 at 22:01














-1












-1








-1








The problem is to solve this.



The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?



I wrote this code



#include <iostream>
#include <math.h>
using namespace std;

bool prime(long int a);

int main()
{
long int b = 600851475143/2;
long int k;



for(long int i = 1; i <= b ; i++)
{
if(b % i == 0 && prime(i) == true)
{
k = i;
}
}
cout << k << endl;
return 0;



}

bool prime(long int a)
{
bool p = true;

for(long int i = 2; i <= sqrt(a) && p == true ; i++)
if(a % i == 0) p = false;

return p;
}


and when I execute after a build, it opens a console , and shows nothing










share|improve this question














The problem is to solve this.



The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?



I wrote this code



#include <iostream>
#include <math.h>
using namespace std;

bool prime(long int a);

int main()
{
long int b = 600851475143/2;
long int k;



for(long int i = 1; i <= b ; i++)
{
if(b % i == 0 && prime(i) == true)
{
k = i;
}
}
cout << k << endl;
return 0;



}

bool prime(long int a)
{
bool p = true;

for(long int i = 2; i <= sqrt(a) && p == true ; i++)
if(a % i == 0) p = false;

return p;
}


and when I execute after a build, it opens a console , and shows nothing







c++ console






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Nov 25 '18 at 21:31









Mane HambardzumyanMane Hambardzumyan

269




269













  • Debuggers are a brilliant tool for solving problems like this. Pop a breakpoint at the start of the program, start up the program, and start start stepping until the program blocks or starts going around in circles.

    – user4581301
    Nov 25 '18 at 21:36











  • g++ spits out warning: overflow in implicit constant conversion [-Woverflow] long int b = 600851475143/2; You should resolve this. Come to think of it, 600851475143/2; is a darn big number. You might want to reconsider using it as a loop bound.

    – user4581301
    Nov 25 '18 at 21:42











  • Regarding the prime computation, this is a brutally slow way to do this. Consider the number of times you are recomputing the i = 2 case.

    – user4581301
    Nov 25 '18 at 21:45











  • I didn't complete the previous thought. Use memoization to reduce the amount of redundant work you have to do. See if you can take advantage of a Prime Number Sieve.

    – user4581301
    Nov 25 '18 at 22:01



















  • Debuggers are a brilliant tool for solving problems like this. Pop a breakpoint at the start of the program, start up the program, and start start stepping until the program blocks or starts going around in circles.

    – user4581301
    Nov 25 '18 at 21:36











  • g++ spits out warning: overflow in implicit constant conversion [-Woverflow] long int b = 600851475143/2; You should resolve this. Come to think of it, 600851475143/2; is a darn big number. You might want to reconsider using it as a loop bound.

    – user4581301
    Nov 25 '18 at 21:42











  • Regarding the prime computation, this is a brutally slow way to do this. Consider the number of times you are recomputing the i = 2 case.

    – user4581301
    Nov 25 '18 at 21:45











  • I didn't complete the previous thought. Use memoization to reduce the amount of redundant work you have to do. See if you can take advantage of a Prime Number Sieve.

    – user4581301
    Nov 25 '18 at 22:01

















Debuggers are a brilliant tool for solving problems like this. Pop a breakpoint at the start of the program, start up the program, and start start stepping until the program blocks or starts going around in circles.

– user4581301
Nov 25 '18 at 21:36





Debuggers are a brilliant tool for solving problems like this. Pop a breakpoint at the start of the program, start up the program, and start start stepping until the program blocks or starts going around in circles.

– user4581301
Nov 25 '18 at 21:36













g++ spits out warning: overflow in implicit constant conversion [-Woverflow] long int b = 600851475143/2; You should resolve this. Come to think of it, 600851475143/2; is a darn big number. You might want to reconsider using it as a loop bound.

– user4581301
Nov 25 '18 at 21:42





g++ spits out warning: overflow in implicit constant conversion [-Woverflow] long int b = 600851475143/2; You should resolve this. Come to think of it, 600851475143/2; is a darn big number. You might want to reconsider using it as a loop bound.

– user4581301
Nov 25 '18 at 21:42













Regarding the prime computation, this is a brutally slow way to do this. Consider the number of times you are recomputing the i = 2 case.

– user4581301
Nov 25 '18 at 21:45





Regarding the prime computation, this is a brutally slow way to do this. Consider the number of times you are recomputing the i = 2 case.

– user4581301
Nov 25 '18 at 21:45













I didn't complete the previous thought. Use memoization to reduce the amount of redundant work you have to do. See if you can take advantage of a Prime Number Sieve.

– user4581301
Nov 25 '18 at 22:01





I didn't complete the previous thought. Use memoization to reduce the amount of redundant work you have to do. See if you can take advantage of a Prime Number Sieve.

– user4581301
Nov 25 '18 at 22:01












2 Answers
2






active

oldest

votes


















0














Add a cout statement inside the for loop in main. Your program is running, it's just taking a long time.






share|improve this answer































    0














    The code is fine. 600851475143/2 is just a large number, so you have to wait some minutes till the result will be printed.
    Further you're testing kind of twice if it a prime which makes the complexity unnecessarily much higher.
    Try this:



    long int b = 600851475143/2;
    long int k = b;
    for(long int i = 2; i < b ; i++)
    {
    if(b % i == 0)
    {
    k = i;
    break;
    }
    }
    cout << k << endl;





    share|improve this answer


























    • I think the problem is given for this. Maybe there is more optimal way to solve this problem ?

      – Mane Hambardzumyan
      Nov 25 '18 at 21:45











    • @ManeHambardzumyan Look into cryptography. Factoring huge numbers into primes is something they do every day and they have a lot of tricks to make it easier to compute.

      – user4581301
      Nov 25 '18 at 21:59













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    2 Answers
    2






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    2 Answers
    2






    active

    oldest

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    active

    oldest

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    active

    oldest

    votes









    0














    Add a cout statement inside the for loop in main. Your program is running, it's just taking a long time.






    share|improve this answer




























      0














      Add a cout statement inside the for loop in main. Your program is running, it's just taking a long time.






      share|improve this answer


























        0












        0








        0







        Add a cout statement inside the for loop in main. Your program is running, it's just taking a long time.






        share|improve this answer













        Add a cout statement inside the for loop in main. Your program is running, it's just taking a long time.







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Nov 25 '18 at 21:38









        SavithruSavithru

        602511




        602511

























            0














            The code is fine. 600851475143/2 is just a large number, so you have to wait some minutes till the result will be printed.
            Further you're testing kind of twice if it a prime which makes the complexity unnecessarily much higher.
            Try this:



            long int b = 600851475143/2;
            long int k = b;
            for(long int i = 2; i < b ; i++)
            {
            if(b % i == 0)
            {
            k = i;
            break;
            }
            }
            cout << k << endl;





            share|improve this answer


























            • I think the problem is given for this. Maybe there is more optimal way to solve this problem ?

              – Mane Hambardzumyan
              Nov 25 '18 at 21:45











            • @ManeHambardzumyan Look into cryptography. Factoring huge numbers into primes is something they do every day and they have a lot of tricks to make it easier to compute.

              – user4581301
              Nov 25 '18 at 21:59


















            0














            The code is fine. 600851475143/2 is just a large number, so you have to wait some minutes till the result will be printed.
            Further you're testing kind of twice if it a prime which makes the complexity unnecessarily much higher.
            Try this:



            long int b = 600851475143/2;
            long int k = b;
            for(long int i = 2; i < b ; i++)
            {
            if(b % i == 0)
            {
            k = i;
            break;
            }
            }
            cout << k << endl;





            share|improve this answer


























            • I think the problem is given for this. Maybe there is more optimal way to solve this problem ?

              – Mane Hambardzumyan
              Nov 25 '18 at 21:45











            • @ManeHambardzumyan Look into cryptography. Factoring huge numbers into primes is something they do every day and they have a lot of tricks to make it easier to compute.

              – user4581301
              Nov 25 '18 at 21:59
















            0












            0








            0







            The code is fine. 600851475143/2 is just a large number, so you have to wait some minutes till the result will be printed.
            Further you're testing kind of twice if it a prime which makes the complexity unnecessarily much higher.
            Try this:



            long int b = 600851475143/2;
            long int k = b;
            for(long int i = 2; i < b ; i++)
            {
            if(b % i == 0)
            {
            k = i;
            break;
            }
            }
            cout << k << endl;





            share|improve this answer















            The code is fine. 600851475143/2 is just a large number, so you have to wait some minutes till the result will be printed.
            Further you're testing kind of twice if it a prime which makes the complexity unnecessarily much higher.
            Try this:



            long int b = 600851475143/2;
            long int k = b;
            for(long int i = 2; i < b ; i++)
            {
            if(b % i == 0)
            {
            k = i;
            break;
            }
            }
            cout << k << endl;






            share|improve this answer














            share|improve this answer



            share|improve this answer








            edited Nov 25 '18 at 21:46

























            answered Nov 25 '18 at 21:41









            goarangoaran

            446




            446













            • I think the problem is given for this. Maybe there is more optimal way to solve this problem ?

              – Mane Hambardzumyan
              Nov 25 '18 at 21:45











            • @ManeHambardzumyan Look into cryptography. Factoring huge numbers into primes is something they do every day and they have a lot of tricks to make it easier to compute.

              – user4581301
              Nov 25 '18 at 21:59





















            • I think the problem is given for this. Maybe there is more optimal way to solve this problem ?

              – Mane Hambardzumyan
              Nov 25 '18 at 21:45











            • @ManeHambardzumyan Look into cryptography. Factoring huge numbers into primes is something they do every day and they have a lot of tricks to make it easier to compute.

              – user4581301
              Nov 25 '18 at 21:59



















            I think the problem is given for this. Maybe there is more optimal way to solve this problem ?

            – Mane Hambardzumyan
            Nov 25 '18 at 21:45





            I think the problem is given for this. Maybe there is more optimal way to solve this problem ?

            – Mane Hambardzumyan
            Nov 25 '18 at 21:45













            @ManeHambardzumyan Look into cryptography. Factoring huge numbers into primes is something they do every day and they have a lot of tricks to make it easier to compute.

            – user4581301
            Nov 25 '18 at 21:59







            @ManeHambardzumyan Look into cryptography. Factoring huge numbers into primes is something they do every day and they have a lot of tricks to make it easier to compute.

            – user4581301
            Nov 25 '18 at 21:59




















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