Question

Write a recursive method isReverse(String s1, String s2) that takes two strings and returns true if s1 is the reverse of s2, false otherwise. Then, draw the sequence of recursive calls for the following cases. Submit your diagrams in a PDF file called isReverseTrace.pdf.

isReverse("happy", "yppah") will return true

isReverse("cool", "loac") will return false

isReverse("", "") will return true

Answer 1

public class IsReverse {

    public static boolean isReverse(String s1, String s2) {
        if(s1.length() != s2.length()) {
            return false;
        } else {
            if(s1.isEmpty()) {
                return true;
            } else {
                return s1.charAt(0) == s2.charAt(s2.length()-1) && isReverse(s1.substring(1), s2.substring(0, s2.length()-1));
            }
        }
    }

    public static void main(String[] args) {
        System.out.println(isReverse("happy", "yppah"));
        System.out.println(isReverse("cool", "loac"));
        System.out.println(isReverse("", ""));
    }
}