Add Binary

Add Binary.java

/*
Given two binary strings, return their sum (also a binary string).

For example,
a = "11"
b = "1"
Return "100".
*/

public class Solution {
    public  String addBinary(String a, String b) {
        int longer = 0;
        int shorter = 0;
        boolean aIsLonger;
        if (a.length() > b.length()) {
            longer = a.length();
            shorter = b.length();
            aIsLonger = true;
        } else {
            longer = b.length();
            shorter = a.length();
            aIsLonger = false;
        }

        char[] result = new char[longer + 1 ];
        char c;
        char d;

        boolean carryOver = false;

        for (int i = 0; i < longer ; i++) {
            if (i >= shorter) {
                if (aIsLonger) {
                    c = a.charAt(a.length() - 1 - i);
                    d = '0';
                } else {
                    c = '0';
                    d = b.charAt(b.length() - 1 - i);
                }
            } else {
                c = a.charAt(a.length() - 1 - i);
                d = b.charAt(b.length() - 1 - i);
            }

            if (c == d) {
                result[result.length - 1 - i] = carryOver ? '1' : '0';
                carryOver = c == '1';
            } else {
                if((c == '1' || d == '1') && carryOver) {
                    result[result.length - 1 - i] = '0';
                    carryOver = true;
                } else {
                    result[result.length - 1 - i] = '1';                
                    carryOver = false;                   
                }     
            }
        }
        
        String toReturn;
        if(carryOver) {
            result[0] = '1';
            toReturn = new String(result);
        } else {
            toReturn = new String(result);
            toReturn = toReturn.substring(1);
        }
        
        return toReturn;
    }
}