Caesar Cipher HackerRank Solution

Caesar Cipher HackerRank Solution
Source : https://www.hackerrank.com/challenges/caesar-cipher-1

Julius Caesar protected his confidential information by encrypting it using a cipher. Caesar's cipher shifts each letter by a number of letters. If the shift takes you past the end of the alphabet, just rotate back to the front of the alphabet. In the case of a rotation by 3, w, x, y and z would map to z, a, b and c.

Original alphabet:      abcdefghijklmnopqrstuvwxyzAlphabet rotated +3:    defghijklmnopqrstuvwxyzabc

For example, the given cleartext and the alphabet is rotated by . The encrypted string is .

Note: The cipher only encrypts letters; symbols, such as -, remain unencrypted.

Function Description

Complete the caesarCipher function in the editor below. It should return the encrypted string.

caesarCipher has the following parameter(s):

• s: a string in cleartext
• k: an integer, the alphabet rotation factor

Input Format

The first line contains the integer, , the length of the unencrypted string.
The second line contains the unencrypted string, .
The third line contains , the number of letters to rotate the alphabet by.

Constraints

is a valid ASCII string without any spaces.

Output Format

For each test case, print the encoded string.

Sample Input

11
middle-Outz
2

Sample Output

okffng-Qwvb

Explanation

Original alphabet:      abcdefghijklmnopqrstuvwxyzAlphabet rotated +2:    cdefghijklmnopqrstuvwxyzabm -> oi -> kd -> fd -> fl -> ne -> g-    -O -> Qu -> wt -> vz -> b

Source : https://www.hackerrank.com/challenges/caesar-cipher-1

Solution

	// Karthikalapati.blogspot.com
	static String caesarCipher(String str, int k) {
	StringBuilder sb = new StringBuilder();
	for (int i = 0; i < str.length(); i++) {
	char ch = str.charAt(i);
	sb.append(encrypt(ch, k));
	}
	return sb.toString();
	}
	/* Encrypts a character using Caesar Cipher */
	private static char encrypt(char ch, int K) {
	if (!Character.isLetter(ch)) {
	return ch;
	}
	char base = Character.isLowerCase(ch) ? 'a' : 'A';
	return (char) ((ch - base + K) % 26 + base);
	}
	// Discuss on HackerRank: https://www.hackerrank.com/challenges/caesar-cipher-1/forum/comments/269393