Question

​​​​​​C++

It may seem hard but the instructions are listed, it's all about loops

• For this part, the program gives the user 4 choices for encrypting (or decrypting) the first character of a file. Non-lowercase characters are simply echoed. The encryption is only performed on lowercase characters.
  • If c is char variable, then islower(c) will return true if c contains an lowercase character, false otherwise
  • To read a single character from a file (let inFile be the name of your ifstream), you can use: inFile.get(c);
    • This will read one character, even the whitespace characters
  • Choice 1 – No encryption, echo the character from the file
  • Choice 2 – Encrypt by shifting. For example, shifting by 3 characters would change an ‘a’ to a ‘d’ because that is 3 letters later. If you reach the end of the alphabet then you need to roll over. For example ‘z’ plus 3 is ‘c’.
    • NOTE: The process of converting the ‘z’ to a ‘c’ should NOT need the use of an if, switch, or loop statement.
    • For this week, you may use an if or switch if you need, but next week you’ll have to do it without
  • Choice 3 – This is the opposite of choice 2. Instead of moving 3 letters forward, it will move 3 letters backwards. A ‘d’ will become ‘a’.
    • Like choice 2, the shifting can be accomplished without if’s, switch’s, and loop’s.
  • Choice 4 – This will calculate a hash value. You sum the ASCII values of all of the characters and at the end of the file print the last 2 digits of the sum. For example, “abc” is 94 because ‘a’ is 97, ‘b’ is 98, ‘c’ is 99, which has a sum of 294.
    • Remember, this week we are only reading a single character
  • Your program should prompt the user for:
    • The encryption type
    • The name of a file
    • For this week, the prompt will be very short, just a ?
  • Your program should output the encrypted characters (or a hash value).
  • file1.txt has the following contents:

yippee

• file2.txt has the following contents:

A-bba cc
xyyz

Sample Run #1 (bold, underlined text is what the user types):

? 1 file1.txt

y

Sample Run #2 (bold, underlined text is what the user types):

? 2 file1.txt

b

Sample Run #3 (bold, underlined text is what the user types):

? 3 file1.txt

v

Sample Run #4 (bold, underlined text is what the user types):

? 4 file1.txt

21

Sample Run #5 (bold, underlined text is what the user types):

? 1 file2.txt

A

Sample Run #6 (bold, underlined text is what the user types):

? 2 file2.txt

A

Sample Run #7 (bold, underlined text is what the user types):

? 4 file2.txt

0

Answer 1

#include <bits/stdc++.h>
using namespace std;

int main(){
   int choice;
   ifstream i;
   string fileName;
   cout<<"? ";
   cin>>choice>>fileName;
   i.open(fileName);
   char c;
   if(choice==1){
       cout<<c;      
   }
   if(choice==2){
       i>>c;
       if(islower(c)){
           int x = c;
           x+=3;
           if(x>122){
               x-=26;
           }
           cout<<(char)x;
       }
       else{
           cout<<c;
       }
   }
   if(choice==3){
       i>>c;
       if(islower(c)){
           int x = c;
           x-=3;
           if(x<97){
               x+=26;
           }
           cout<<(char)x;
       }
       else{
           cout<<c;
       }
   }
   if(choice==4){
       int x=0;
       while(i>>c){
           x+=(int)c;
       }
       cout<<(x%100);
   }
   return 0;
}

The main idea of the code lies in the fact that typecasting a char value to int by writing the (int) before it returns the ascii value of the character.