#include<stdio.h>
#include<malloc.h>
#include<conio.h>
int main()
{
char alpha[]={'?','A','B','C','D','E','F','G','H','I','J','K','L','M',
'N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
int n,i,pos,r,tmp,j,flag=1;
long int tot=0;
char *combination;
printf("\n Enter the number of objects (max value is 26):");
scanf("%d",&n);
printf("\n Enter the value of r ( 1<= r <= n):");
scanf("%d",&r);
combination =(char *)malloc(n*sizeof(char));
for(i=1;i<=n;i++)
combination[i]=alpha[i];
printf("\n The combinations are (is):\n");
printf("\t\t ");
for(i=1;i<=r;i++)
printf("%c",combination[i]);
tot=1;
while(flag)
{
for(i=r;i>=1;i--)
{
if(combination[i]-64==n-r+i)
{
}
else
{
pos=i;
break;
}
}
if(i==0)
{
flag=0;
break;
}
for(j=1;j<=26;j++)
if(combination[pos]==alpha[j])
break;
combination[pos]=alpha[j+1];
for(i=pos+1;i<=r;i++)
combination[i]=alpha[(combination[i-1]-64)+1];
printf("\n");
printf("\t\t ");
for(i=1;i<=r;i++)
printf("%c",combination[i]);
tot++;
}
printf("\n Total number of combination is: %ld",tot);
return 0;
}
