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WRITE A PROGRAM FOR MAGIC SQUARES

Posted on 1997-09-07
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WRITE A PROGRAM THAT GENERATES A MAGIC SQUARE BY THE FOLLOWING METHOD.  AN 5X5, AN 7X7, AND A 3X3 SQUARE.  THE SUM OF EVERY ROW, THE SUM OF EVERY COLUMN AND THE SUM OF THE TWO DIAGONALS MUST BE EQUAL FOR A SQUARE TO BE MAGIC.

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Question by:tester090797
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by:ozo
ID: 1254234
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Slarti earned 200 total points
ID: 1254235
This sounds like a high-complexity problem, but there is a very simple solution for the particular case of odd-length magic squares. The following program illustrates this solution. It is written for Borland C++ using only ANSI C commands, so you should have no problems porting it.

------- BEGIN PROGRAM CODE
#include <stdio.h>
#include <mem.h>

#define MAXN 9
typedef int Square[MAXN][MAXN];

int main() {
      Square s={{0}};
      int i,x,y,xnew,ynew,n;

      /* get length of square */
      do {
            printf("Type length of square (odd number between 3 and %d): ",MAXN);
            scanf("%d",&n);
      } while(n%2==0 || n<3 || n>MAXN);

      /* calculate magic square */
      x=0;
      y=n/2;
      for(i=0; i<n*n; i++) {
            /* place current value */
            s[x][y]=i+1;
            /* find next spot */
            xnew = (x+n-1)%n;
            ynew = (y+n-1)%n;
            if(s[xnew][ynew]==0) {
                  x=xnew;
                  y=ynew;
            } else
                  x=(x+1)%n; /* y remains the same */
      }

      /* display result */
      for(y=0; y<n; y++) {
            for(x=0; x<n; x++)
                  printf("%d\t",s[x][y]);
            printf("\n");
      }

      return 0;
}
------- END PROGRAM CODE

That's it. The complexity is proportional to n - you can't do it any faster than that. You can, of course, create larger squares by increasing the value of MAXN.

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by:Slarti
ID: 1254236
Sorry, my mistake. The complexity is proportional to n squared. But I still think you won't be able to make it any faster.
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by:tester090797
ID: 1254237
THANK YOU!  I BEING A WEEKEND WARRIOR ON LEARNING HOW TO PROGRAMM IN 'C' FOUND THE SOLUTION TO BE VERY USEFUL.  SOME BOOKS I'VE PURCHASED IS ARE EITHER USEFUL OR TOO "TECH."  I'M USING MICROSOFT VISUAL C/C++ 5.0, THE ONLY THING I HAD TO DO TO GET RID OF AN COMPILE ERROR WAS TO REMOVE #INCLUDE <MEM.H> AND IT DID ITS THING.
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