题目要求：将两个二进制字符串相加结果以二进制字符串的形式返回

/** * @author rale *  * Given two binary strings, return their sum (also a binary string). * For example, * a = "11" * b = "1" * Return "100". */public class AddBinary {        public String addBinary(String a, String b) {        StringBuilder result = new StringBuilder();        int pointerA = a.length()-1;        int pointerB = b.length()-1;        int carry = 0;        while(pointerA>=0 || pointerB>=0){            int sum = carry;            if(pointerA>=0){                sum += (a.charAt(pointerA)-'0');                pointerA--;            }            if(pointerB>=0){                sum += (b.charAt(pointerB)-'0');                pointerB--;            }            result.append(sum%2);            carry = sum/2;        }        if(carry!=0){            result.append('1');        }        return result.reverse().toString();    }}