Combination in Lexicographical Order

#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;

}