Question

I have been stumped on this for a long time and I was wondering if anyone can help me out. How could I write a program that would calculate the shift value of an encrypted Caesar’s Cypher file in C++? My assignment is to take each lower case letter and calculate how many times each is used, then find the most frequent character. I know I can do that with a map of char and int. But then I would have to go back to that letter to change it to the letter ‘e’. With maps there’s no way to search back through values. I think the only way is a vector of vectors but I wouldn’t know how to find the letter again with those either. Does anyone know a better way or how could I use vectors to accomplish this?

Answer 1

You can go like this.

1. First read whole file in a buffer.
2. Create map with char key and int value. with all alphabets and values 0

3. Loop over whole buffer till end incrementing value in map by 1 for each character. Also maintain max variable storing key ha of character having maximum value.

4. At end of loop max variable will point to e.

5. Subtracting 4 from max will give you shift value for this cipher. If it comes negative then you can add 26. (As this calculation in in mod 26)