Thread: Caesar Cipher help!!

Hi i am having problem with strings using for loop. When i enter input abc, strlen shows that string length is 3 but when i enter abc d string length still shows 3 and i think loop stop when it sees space.

here is my program

Code:

/* Caesar Cipher 
   Darshan
 */

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

int main(){
    
    // Message to be encrypted
    char input[80];
    
    // shift
    int key =0;

    int i;
    
    // Enter shift amount
    printf("Enter shift amount (1-25): ");
    scanf("%d", &key);
    
    // enter message
    printf("Enter message to be encrypted: ");
    scanf("%s", &input);
    

    for(i=0; input[i] != '\0';i++)
    {
        // check  if letter is captial or lower case
        if (input[i]>='A' && input[i]<='Z')
        {
            input[i] = (input[i] - 'A' + key) % 26 + 'A';
        }
            else 
                if (input[i]>='a' && input[i]<='z')
                {
                    input[i] = (input[i] - 'a' + key) % 26 + 'a';
                } 

    }
    
    printf("\nEncrypted message: %s", input);
    printf("\nstrlen(%lu)", strlen(input));
    
    getchar();
    getchar();
    return 0;   
    
}

Thanks for your help

Which is just one of the reasons scanf() is not well suited at all for user input.

fgets() is preferred, but try this scanf() format out, and see what you think.

Code:

      scanf("%[^\n]s",input);
      
      printf("%s  %d", input, strlen(input));

that didn't work for me but is this right if i do this

Code:

   if (input[i] == ' ')
        {
            input [i] = ' ';
        }

inside for loop? b/c its still not working.

if i let

Code:

char input[80] = abc xyz;

without asking user to enter any input it works fine but it doesn't work when i ask user to enter string.

Originally Posted by darshan10

Hi i am having problem with strings using for loop. When i enter input abc, strlen shows that string length is 3 but when i enter abc d string length still shows 3 and i think loop stop when it sees space.

here is my program

Code:

/* Caesar Cipher 
   Darshan
 */

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

int main(){
    
    // Message to be encrypted
    char input[80];
    
    // shift
    int key =0;

    int i;
    
    // Enter shift amount
    printf("Enter shift amount (1-25): ");
    scanf("%d", &key);
    
    // enter message
    printf("Enter message to be encrypted: ");
    scanf("%s", &input);
    

    for(i=0; input[i] != '\0';i++)
    {
        // check  if letter is captial or lower case
        if (input[i]>='A' && input[i]<='Z')
        {
            input[i] = (input[i] - 'A' + key) % 26 + 'A';
        }
            else 
                if (input[i]>='a' && input[i]<='z')
                {
                    input[i] = (input[i] - 'a' + key) % 26 + 'a';
                } 

    }
    
    printf("\nEncrypted message: %s", input);
    printf("\nstrlen(%lu)", strlen(input));
    
    getchar();
    getchar();
    return 0;   
    
}

Thanks for your help

What happens if they type a number?

i fixed my string problem using

Code:

fgets(message, 80, stdin);

now i want to know that how can i make it invalid shift when someone enter char instead of number

Code:

  
while(key <1 || key > 25)
    {
        printf("Enter shift amount between (1-25): ");
        scanf("%d", &key);
    }

i have tried using this b/c it don't work

Code:

  while(key == getchar())
    {
        printf("Enter shift amount between (1-25): ");
        scanf("%d", &key);
    }

thanks

Code:

do {
   printf("\nEnter shift amount between (1-25): ");
   scanf("%d", &key);
   getchar();
   if(key < 1 || key > 25) {
      key = 0;
      printf("Invalid input, key now changed to %d\n", key);
   }
}while(!key);

Handles letter entry, also