//To print all possible permutations of string

#include<stdio.h>

#include<string.h>

#include<math.h>

//Integer to binary representation

void toBinary(int i,int n,char * str)

{

int j,k,temp,pos=0;

temp=i;

pos=n-1;

while(temp!=0)

{

//str[pos--]=(temp%2==1)?49:48;

if(temp==1)

{

str[pos]=49;

break;

}

if(temp%2==0)

str[pos--]=49;

else

str[pos--]=48;

temp/=2;

}

}

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 && a[0]!=0)

printf("%s\n", a);

else

{

for (j = i; j <= n; j++)

{

swap((a + i), (a + j));

permute(a, i + 1, n);

swap((a + i), (a + j)); //backtrack

}

}

}

/*

int main(){

char a[] = { "abcd" };

permute(a, 0, 3);

getchar();

return 0;

}

*/

int main()

{

int i, j, n, num, ctr;

char * str, **all_sets;

char * temp_str;// = (char *)malloc(sizeof(char)*n);

printf("Enter num of chars in string: ");

scanf("%d",&n);

scanf("%c", &j);

num=(int)pow((double)2,(double)n);

printf("Enter a string: ");

str=(char *) malloc(sizeof(char)*(n+1));

temp_str = (char *)malloc(sizeof(char)*(n+1));

str[n]=0;

for(i=0;i<n;i++)

{

scanf("%c",&str[i]);

}

all_sets=(char **) malloc(sizeof(char *) * num);

for(i=0;i<num;i++)

{

all_sets[i]=(char *) malloc(sizeof(char)*(n+1));

memset(all_sets[i],48,n);

all_sets[i][n]=0;

toBinary(i,n,all_sets[i]);

}

for(i=0;i<num;i++)

{

ctr = 0;

memset(temp_str, 0, n+1);

//printf("%s\n",all_sets[i]);

for(j=0;j<n;j++)

{

if (all_sets[i][n - j - 1] == 49){

temp_str[ctr++] = str[j];

}

//printf("%c",str[j]);

}

if (temp_str[0] != 0){

permute(temp_str, 0, ctr-1);

//printf("%s\n", temp_str);

}

}

return 0;

}