How to check if two strings are permutation?

general
1

#include<stdio.h>
#define ALPHABET 26
int main ()
{
char string[ALPHABET] = “abcdefghijkmnlopqrstuvwxyz”;
char perm [ALPHABET];
int i;
int distance;
int flag=1;
printf(“Enter ABC permutation\n”);
for(i=0;i<ALPHABET;i++)
{
scanf("%c",& perm[i]);
}

distance = (int)perm[0] - (int)string;

for(i=0;i<ALPHABET;i++)
{

     if ( ((int)perm[i] - (int)string[i]) != distance )
    {
    flag = 0;
    break;
    }
   }

  if (flag)
  {

printf("your input is invalid permutation\n");
   }


else


{
printf("your input is valid permutation\n");
}

 return 0;
 }

Hi guys I need to write a code which has to check if a certain order of alphabetic letters is a permutation of the alphabetic letters in normal order.My problem is that I dont know how to print an error massage for wrong permutations like if I enter similar letters at least two times then its not a permutation.
Another example is when there is at least one capital letter or one number in the array perm[ALPHABET] then it has to print the error massage"your input is invalid permutation" so how do I do it in my code?
the idea for a valid input is this for example:
input :- abcdfehgikjmnlpoqsrtvuxwzy is a permutation of the whole 26 letters.
while inputs like writing the letter q 26 times or Abcdefghijkmnlopqrstuvwxyz or 1bcdefg6ijkmnlopqrstuvwxyz is wrong.

2

Simplest method to check if two strings are anagrams would be to sort the characters in the strings and compare them.