What's wrong with this C program

Question

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Help with C puzzle

The intention of the program was to print a minus sign 20 times, but it doesn't work.

  #include <stdio.h>
  int main()
  {
      int i;
      int n = 20;
      for( i = 0; i < n; i-- )
          printf("-");
      return 0;
  }

Answer 1

 #include <stdio.h>
  int main()
  {
      int i;
      int n = 20;
      for( i = 0; i < n; i++ )
          printf("-");
      return 0;
  }

You had -- instead of ++

Answer 2

Replace i-- with i++.

Answer 3

int main() { 
  int i; 
  int n = 20; 
  for( i = 0; i < n; i++)
    printf("-"); 
  return 0; 
}

You had decrement instead of increment.

Answer 4

Have you tried changing the

i--

to

i++

You have the loop to print out a "-" for as long as "i" is less than 20. After every loop you reduce the value of i by 1, it will continue to print for a very long time. Changing the final part of the for loop to "i++" means it will perform one iteration each loop and stop once the twentieth iteration finished.

Answer 5

the i-- needs to be i++

you could also do

 int n = -20;
  for( i = 0; i > n; i-- )

but that is bad coding practice

Answer 6

You'll print no dashes. You can either go with Jaime Wong's solution or do this:

for (i = n; i >= 0; i--)

Answer 7

Change i-- to i++. i-- decrements the value which at start is 0 and with subsequent reductions won't ever reach 20 (or +20).

Answer 8

This is a classic puzzle!

The way I saw it was

"You can only change/insert/delete one character in the code to make the - print 20 times".

Some answers are (if I remember them correctly)

1)

 #include <stdio.h> 
  int main() 
  { 
      int i; 
      int n = 20; 
      for( i = 0; -i < n; i-- ) 
          printf("-"); 
      return 0; 
  }

Here you change the i < n to -i < n

2)

 #include <stdio.h> 
  int main() 
  { 
      int i; 
      int n = 20; 
      for( i = 0; i < n; n-- ) 
          printf("-"); 
      return 0; 
  }

Here you change the i-- to n--

3)

 #include <stdio.h> 
  int main() 
  { 
      int i; 
      int n = 20; 
      for( i = 0; i + n; i-- ) 
          printf("-"); 
      return 0; 
  }

You change the i < n to i+n.

For a challenge, try changing/inserting/deleting one character to make it print the - 21 times. (Don't read the comments to this answer if you want to try it!)

Answer 9

What exactly are you trying to do with this problem??? Here you are trying to decrement the value of a variable..a variable whose value will never reach the condition (i<20) you have provided... hence it will keep on printing '-' until what jamie wong specified, i.e. i= -2^31. It will become +ve. I just tried this program.

#include <stdio.h>
int main()
{
    int i;
    int n = 20;
    for( i = 0; i < n; i-- )
        printf("-");
    return 0;
}

According to the question you asked, i should be incremented, i.e. i++ instead of i--.

@jamie wong: thanx man..learnt a new thing about tht a wraparound....