Expert: vijayan - 11/30/2008

Question
hi
i have a problem whit the code below,in the rows that i have signed the code i want the program to search trough the mark[i][j] to find that if we have any array with i row and j column that contain '0' but in it's first search it just search for i=m/2 & j=n/2 that i initialaized in the bug function,but i want it to compare all of the arrays and it just compare '0' whit i=m/2 &j=n/2 can you help me about this problem?



#include <stdlib.h>
#include <time.h>
#include<string.h>
#include<stdio.h>

void bug(int x,int y);
int mark[10][10],m,n;
void main()
{
  int j=0,i=0,w=0,x=0,y=0;
  printf("Enter m&n:1<m<41,1<n<21\n");
  scanf("%d%d",&m,&n);
  
  for(i=1;i<=m;i++)
     for(j=1;j<=n;j++)
        mark[i][j]=0;

     m=m+1;
     n=n+1;

  i=0;
  for(j=0;j<=n+1;j++)
      mark[i][j]='#';

    i=n+1;
  for(j=0;j<=n+1;j++)
     mark[i][j]='#';
  j=0;
  for(i=0;i<=m+1;i++)
     mark[i][j]='#';
  j=m+1;
  for(i=0;i<=m+1;i++)
     mark[i][j]='#';

  
  do{
     for(i=1;i<=m-1;i++)//*<-------------------my problem
          for(j=1;j<=n-1;j++){//*<-------------------my problem
            if(mark[i][j]==0)//*<-------------------my problem
               w=0;
            else
               w=1;
          }
          printf("w=%d\n",w);
           bug(x,y);
       }while(w!=1);
}
void bug(int x,int y){
  int count=0,stor1[50],stor2[50],a=0,b=0;
  int k = 1 + int( 9.0 * ( rand()  /  ( RAND_MAX + 1.0 ) ) ) ;
  x=m/2;
  y=n/2;
  mark[x][y]=1;
         printf("k=%d\n",k);

       if(k==1){
          x=x-1;
          y=y+1;
          count++;
       }
       else if(k==2){
          y=y+1;
          count++;
       }
       else if(k==3){
          x=x+1;
          y=y+1;
          count++;
       }
       else if(k==4){
          x=x+1;
          count++;
       }
       else if(k==5){
          x=x+1;
          y=y-1;
          count++;
       }
       else if(k==6){
          y=y-1;
          count++;
       }
       else if(k==7){
          x=x-1;
          y=y-1;
          count++;
       }
       else if(k==8){
          x=x-1;
          count++;
       }

       stor1[a]=x;
       stor2[b]=y;

       a++;
       b++;

       if(mark[x][y]=='#'){

          x=stor1[a-2];
          y=stor2[b-2];

       }

       mark[x][y]=1;

       
       printf("x=%d,y=%d,count=%d\n",x,y,count);
}


thanx
Bita

Answer
you are causing a buffer overflow for the array mark

int mark[10][10],m,n;

void main()
{
   int j=0,i=0,w=0,x=0,y=0;
   printf("Enter m&n:1<m<41,1<n<21\n");
   scanf("%d%d",&m,&n);

   for(i=1;i<=m;i++)
       for(j=1;j<=n;j++)
           mark[i][j]=0; // i, j could be greater than 9 here

you need mark to be at least

   int mark[40][20],m,n;

m, n could have been corrupted because of the buffer overflow.

otherwise, i cannot see the problem
"i want the program to search trough the mark[i][j] to find that if we have any array with i row and j column that contain '0' but in it's first search it just search for i=m/2 & j=n/2 that i initialaized in the bug function,but i want it to compare all of the arrays and it just compare '0' whit i=m/2 &j=n/2"

i modified mark as suggested above and ran the program.
it seems to go through the entire array in the loop.
just to check out, i added a printf in the loop:
      do{
              for(i=1;i<=m-1;i++)//*<-------my problem
                        for(j=1;j<=n-1;j++){//*<-------my problem
                        {
                               printf( "*** %d %d\n", i, j ) ; // *** added ***
                               if(mark[i][j]==0)//*<-------my problem
                                       w=0;
                               else
                                       w=1;
                        }
                        }
                        printf("w=%d\n",w);
                    bug(x,y);
                }while(w!=1);

and i tested it for some cominations of m and n. eg:

>./a.out
Enter m&n:1<m<41,1<n<21
4 6                    
*** 1 1
*** 1 2
*** 1 3
*** 1 4
*** 1 5
*** 1 6
*** 2 1
*** 2 2
*** 2 3
*** 2 4
*** 2 5
*** 2 6
*** 3 1
*** 3 2
*** 3 3
*** 3 4
*** 3 5
*** 3 6
*** 4 1
*** 4 2
*** 4 3
*** 4 4
*** 4 5
*** 4 6
w=1
k=1
x=1,y=4,count=1