Functions with Loops in C - Overclock.net

Fatal05 · 3 Weeks Ago

Well here I've created some code that prints a hollow rectangle, coarse and fine checkerboard. The only thing is, is that I need to create another function to reduce the number of loops in the entire program 9. I currently have 13 loops.

Needless too say, I'm stuck. I was wondering where I should put this function and could you give me an idea of what its structure should look like?

I believe I need to create a function that prints X's and blank spaces ("X", " ").

Halp.

Code:

#include <stdio.h>

void hollowRect(int width, int height){
   int row, col;

   printf("Hollow rectangle:\n");

   // First row
   for (col = 0; col < width; col++)
      printf("X");

   // Second row
   for (row = 0; row < height-2; row++){
      printf("\nX");
      for (col = 0; col < width-2; col++)
         printf(" ");
      printf("X");
   }

   // Last row
   printf("\n");
   for (col = 0; col < width; col++)
      printf("X");
}

void coarseCheckr(int width, int height){
    int row, col;

    printf("\n\nCoarse Checkerboard:\n");

   // Top Half

   for (row = 0; row < (height/2); row++){
   // Top Left
      for (col = 0; col < (width/2); col++){
         printf("X");
      }
   // Top Right
      for (col = (width/2); col < width; col++){
         printf(" ");
      }
      printf("\n");
   }

   // Bottom Half

   for (row = (height/2); row < height; row++){
   // Bottom Left
      for (col = 0; col < (width/2); col++){
         printf(" ");
      }
   // Bottom Right
      for (col = (width/2); col < width; col++){
         printf("X");
      }
      printf("\n");
   }
}

void fineCheckr(int width, int height){
   int row, col;

  printf("\nFine Checkerboard:\n");

   width += width%2;
   height += height%2;
   for (row = 0; row < height; row++){
      for (col = 0; row%2 == 0 && col < width; col+=2){
         printf("X ");
      }
      for (col = 0; row%2 == 1 && col < width; col+=2){
         printf(" X");
      }
      printf("\n");
   }
}
int main()
{
    int row, col, height, width;

    printf("Enter Height and Width:");
    scanf("%d%d", &height, &width);

    while (height < 2 || width < 2){
       printf("Please enter at least 2 for height and width: ");
       scanf("%d%d", &height, &width);
   }

   hollowRect (width, height);
   coarseCheckr (width, height);
   fineCheckr (width, height);
}

dharmaBum · 3 Weeks Ago

Reduce number of loops as in:
i) Make the code more efficient by reducing the number of executed loops
or
ii) Trim the number of code lines?

(ii) seems most likely so I'll do that, but if it's (i) I'll look more closely.

Quote:

I believe I need to create a function that prints X's and blank spaces ("X", " ").

You can do this, but there is a simpler way to limit the number of loops here.

You have:

Code:

   //first row
   for (col = 0; col < width; col++)
      printf("X");

   // Second row
   for (row = 0; row < height-2; row++){
      printf("\nX");
      for (col = 0; col < width-2; col++)
         printf(" ");
      printf("X");
   }

   // Last row
   printf("\n");
   for (col = 0; col < width; col++)
      printf("X");

Notice that here we loop over the same interval twice (the "top" and "bottom" lines), and for each row we basically repeat that interval with two less (the nested loop). This can be gathered up into one loop statement (the inner loop) with an "if/else" (or otherwise similar) check to see if we're "at the sides." (This can be done a few different and probably more efficient ways but I'm lazy and only give the clearest)

A simplification of the above code:

Code:

row=height;
col=width;
for(int i=0;i<row;i++)
{
   for(int j=0;j<col;j++)
   {
     //if we're at the "top" (i=0), "bottom" (i=row-1),
     //"left" (j=0) or "right" (j=col-1) then print an "X".
     if(i==0 || i==row-1 || j==0 || j==col-1) printf("X");
     //otherwise, print a " ".
     else printf(" ");
    }
    //We've taken care of this row.  Let's start a new one
    printf("\n");
}
//We've reduced four for loops to two!

This can be carried out with the same idea in the other sections of you're code. For example:

Code:

      for (col = 0; row%2 == 0 && col < width; col+=2){
         printf("X ");
      }
      for (col = 0; row%2 == 1 && col < width; col+=2){
         printf(" X");
      }

Can be made into one for loop, using a conditional statement inside the loop to check if the modulus is 1 or 2.

As I indicated at the start, this doesn't actually reduce the number of instructions sent to the CPU. This is a code-readability scheme, because it's easier to look at one loop that does several things than several loops that do one thing (although to the computer these are identical procedures.)

Edit: kept variable names consistent, syntax errors.

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Functions with Loops in C

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