View source for Printing A ← Printing A

Imagine you have a special keyboard with the following keys:

A

Ctrl+A

Ctrl+C

Ctrl+V

where CTRL+A, CTRL+C, CTRL+V each acts as one function key for “Select All”, “Copy”, and “Paste” operations respectively.

If you can only press the keyboard for N times (with the above four keys), please write a program to produce maximum numbers of A. If possible, please also print out the sequence of keys. That is to say, the input parameter is N (No. of keys that you can press), the output is M (No. of As that you can produce).

Solution by Arjun Suresh[edit]

<syntaxhighlight lang="c" name="printa">

1. include <stdio.h>

int main() {

   unsigned long N, M, i;
   printf("Enter N: ");
   scanf("%lu", &N);
   printf("\n\nKey Sequences:\n\n");
   if(N <= 6)
   {
       M = 6;
       for(i = 0; i < N; i++)
       printf("A\n");
   }

   else if (N % 3 == 0)
   {
       M = 3 * (1L<< (N-3)/3); //1<<x gives pow(2,x) and I'm too lazy to include math.h
       for(i = 0; i < 3; i++)
           printf("A\n");
       for(i = 1; i < N/3; i++)
       {
           printf("\nCTRL+A\n");
           printf("CTRL+C\n");
           printf("CTRL+V\n\n");
       }
   }

   else 
   {
       M = 4 * (1L << (N-4)/3) + (N-4)%3; //1<<x gives pow(2,x)
       for(i = 0; i < 4; i++)
           printf("A\n");

       for(i=0; i < (N-4)/3; i++)
       {
           printf("\nCTRL+A\n");
           printf("CTRL+C\n");
           printf("CTRL+V\n\n");
       }

       for(i = 0; i < N%3; i++)
           printf("A\n");
   } 
   printf("\nM = %lu\n", M);

} </syntaxhighlight>