package test2;


public class Utility2B {
	
	private Utility2B() {
		
	}

	/**
	 * Returns the string formed by concatenating the argument
	 * strings s and t with a separator string between them.
	 * For example:
	 * 
	 * <pre>
	 * Utility2B.join("abc", "xyz", ":")
	 * </pre>
	 * 
	 * returns the string <code>"abc:xyz"</code>.
	 *  
	 * @param s a non-null string
	 * @param t a non-null string
	 * @param sep a non-null separator string
	 * @return the string formed by concatenating s followed by
	 * sep followed by t
	 */
	public static String join(String s, String t, String sep) {
		return s + sep + t;
	}
	
	
	/**
	 * Computes the number of characters that are different in
	 * two strings of equal length. The strings are compared
	 * character by character and the number of characters that
	 * differ is returned. For example:
	 * 
	 * <pre>
	 * Utility2B.distance("talk", "talk")    returns  0
	 * Utility2B.distance("talk", "walk")    returns  1
	 * Utility2B.distance("well", "walk")    returns  2    
	 * Utility2B.distance("pick", "walk")    returns  3
	 * Utility2B.distance("zzzz", "walk")    returns  4
	 * </pre>
	 * 
	 * @param s a non-null string
	 * @param t a non-null string
	 * @return the number of characters that differ between s and t
	 * @throws IllegalArgumentException if s and t have different lengths
	 */
	public static int distance(String s, String t) {
		if (s.length() != t.length()) {
			throw new IllegalArgumentException();
		}
		int d = 0;
		for (int i = 0; i < s.length(); i++) {
			if (s.charAt(i) != t.charAt(i)) {
				d++;
			}
		}
		return d;
	}

	
	/**
	 * Returns true if a string is a palindrome. A string is a
	 * palindrome if it contains the same sequence of characters
	 * when read forwards or backwards. For example, the following
	 * strings are all palindromes:
	 * 
	 * <pre>
	 * "noon"
	 * "level"
	 * "racecar"
	 * </pre>
	 * 
	 * <p>
	 * The empty string is considered to be a palindrome.
	 * 
	 * @param s a non-null string
	 * @return true if s is a palindrome and false otherwise
	 */
	public static boolean isPalindrome(String s) {
		/*
		int n = s.length() / 2;
		for (int i = 0; i < n; i++) {
			char c = s.charAt(i);
			char d = s.charAt(s.length() - 1 - i);
			if (c != d) {
				return false;
			}
		}
		return true;
		*/
		
		int k = s.length();
		int counter = 0;
		int u = k-1;
		for (int i =0; i<=(k-1); i++){
			if (s.charAt(i)==s.charAt(u-i)){
				counter += 1;
			}
		}
		if(counter==k){
			return true;
		}return false;
	
	}
	
}