CODEWITHSUNDEEP
c
Engineer
Engineer

Reputation: 161

Global value not getting reflected

I'm trying to generate permutations of a string and store them in a pointer array

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

int count; 
char *str[100];

/* Function to swap values at two pointers */
void swap (char *x, char *y)
{
    char temp;
    temp = *x;
    *x = *y;
    *y = temp;
}

/* Function to print permutations of string
   This function takes three parameters:
   1. String
   2. Starting index of the string
   3. Ending index of the string. */
void permute(char *a, int i, int n) 
{
   int j; 
   if (i == n)
     {
        str[count++]=a;
        printf("%s\n", str[count-1]);
     }    

   else
   {
        for (j = i; j <= n; j++)
       {
          swap((a+i), (a+j));
          permute(a, i+1, n);
          swap((a+i), (a+j)); //backtrack
       }
   }
} 


/* Driver program to test above functions */
int main()
{
   char a[] = "ABC";
   int i;

   count=0;

   permute(a, 0, 2);

   for(i=0;i<count;i++)
      printf("%s\n", str[i]);

   return 0;
}

When I execute this, I get output as:

ABC ACB BAC BCA CBA CAB

ABC ABC ABC ABC ABC ABC

Why am i getting these different values for str in different functions?

Solved:

str[count++]=strdup(a);

or

converted *str[] to str[][] and then did strcpy(str[],a)

Upvotes: 0

Views: 69

Answers (1)

Colin Phipps
Colin Phipps

Reputation: 908

You are editing 'a' in place. You should make a copy of each resulting permutation.

str[count++]=strdup(a);

Upvotes: 3

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