There are exactly 7 locations in your code, which could get the segmentation faults:

1)
Two locations at the code below:

Code:

	str [j][i]='\0';                                                        
	printf("string=%s\n", str[j]);

Reason: Your decleration for str

Code:

      char str[1][624];

Gives you only 1 column of 624 character locations; should be accessible in the code only at the zeroth row location only, like [I]str[0].

Soln: Either make sure that the value of J is not more than 0 and check for

Code:

if(1 == J) break;

//instead of the below;

if(j ==2)
          break;

or declare str like the following

Code:

char str[3][624];

This way you'd not get seg-11 at either of the 2 locations, described above.

2)
Five locations at the following code segments:

Code:

free(str);                                                               
free(c);                                                                 
free(i);                                                                 
free(j);                                                                 
free(flag);

Reason:
You should use free() only on pointers, you explitly declared and defined in your program. That too, only when these pointers are pointing to a valid memory locations on the heap area of your program. Primarily once for every explicit call to malloc(), realloc(), calloc() only, however, sometimes you get a memory allocated through library function calls or some systems call (like stat()) for eg, but here too, such functions require you to pass a validly defined pointers to them.

You should NEVER call free() on any other things. Here you have called free() over a number of datatypes (which contain some numeric values which gets type casted implicitly to pointers to a memory locations which is definitely out of range of your process memory area. Hence getting segmentation faults.

Soln:
Remove the call to free() you do not require them in your program.

Cheers