Sean's Encryption Quest!

One day Sean's friend John wanted him to encrypt a few messages that were to be sent via a TELEGRAM group, so that everyone could see the message, but only those special people who knew decryption can actually understand it. Help Sean write a code that take input values of the type of encryption, a key, and a message to be encrypted that had something to do with the key. 

Input Format: 

1. First line containing the type of encryption X. 
2. Second line containing the key K. 
3. Third line containing the message M. 

Output Format: The first line contains the encrypted message. 

NOTE: The encryption process is based on the simple logic of ADDITION, that is simply adding the value of the key(/modified key) to the characters of the message to be encrypted. ONLY UPPER CASE alphabets need to be considered. X is a number -1 or 0 or 1, 

a) -1 denotes the decreasing value of the key, 

b) 0 denotes the constant value of the key, 

c) 1 denotes the increasing value of the key 

d) In case of invalid input value of X simply display “Invalid Input”. 

If the input value of K is less than or equal to 0, make the initial value of K as 1

Boundary Conditions: The maximum length of the message M is 200 and it's minimum length is 1 

Example Input/Output 01: 

Input: 

1 

2 

SUMMER 

Output:

UXQRKY 

Explanation: Every time the key is used on a character its value is incremented by 1 

Example Input/Output 02: 

Input: 

-1 

6 

HOLIDAY 

Output: 

NTPLFBY 

Explanation: Every time the key is used on a character its value is decremented by 1 

Example Input/Output 03: 

Input: 

0

2

ENTERTAINMENT 

Output: 

GPVGTVCKPOGPV 

Example Input/Output 04: 

Input: 

-1 

1 ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ 

Output: AZYXWVUTSRQPONMLKJIHGFEDCBAZYXWVUTSRQPONMLKJIHGFEDCBAZYXWVUTSRQPONMLKJIHGFEDCBAZYXWVUT

Source Code: 

#include<stdio.h>

#include <string.h>

int main()

{

char s[200];

int x,k,i,a=0,c=0;

scanf("%d %d",&x,&k);

scanf("%s",s);

if(k<=0)

    k=1;

if(x==-1)

{

    for(i=0;i<strlen(s);i++)

    {

        if(k<c*-25)

            s[i]=(((s[i]-'A')+k+(c+1)*26)%26)+65;

        else

            s[i]=(((s[i]-'A')+k)%26)+65;

        a++;

        k--;

        if(a==26)

        {

            c++;

            a=0;

        }

    }

    printf("%s",s);

}

else if(x==1)

{

    for(i=0;i<strlen(s);i++)

    {

        s[i]=(((s[i]-'A')+k)%26)+65;

        k++;

    }

    printf("%s",s);

}

else if(x==0)

{

    for(i=0;i<strlen(s);i++)

        s[i]=(((s[i]-'A')+k)%26)+65;

    printf("%s",s);

}

else

    printf("Invalid Input");

}