Permutations of a String

[theausum]

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

void permute(char *str,int l,int pos,int r);
void swap(char &a,char &b);
void print_string(char *str,int r);

int main()
{
char str[10]="";
int l,r;
printf("Enter The String : ");
gets(str);
l=strlen(str);
printf("Enter The Number Of Places To permute on : ");
scanf("%d",&r);
printf("The Following Permuations are possible : \n\n");
permute(str,l,1,r);
getch();
return 0;
}

void permute(char *str,int l,int pos,int r)
{
//If lock position is on the next character
//than the limit
if(pos==r+1)
{
print_string(str,r); //print - these are the elements//
printf(" ");
return; //and return//
}
//true subscript of character in array is pos-1//
for(int i=pos-1;i<=l-1;i++)
{
//swap the first letter with all next letters
str[pos-1]=str[pos-1]+str[i]-(str[i]=str[pos-1]);
permute(str,l,pos+1,r);
//restore the swap{swap : a=a+b-(b=a)}
str[pos-1]=str[pos-1]+str[i]-(str[i]=str[pos-1]);
}
}

void print_string(char *str,int r)
{
for(int i=0;i<r;i++)
printf("%c",str[i]);
}