题目

思路：从低位加到最高位，相加之和sum % 2；进位 carry = sum / 2；最后反向输出。

public static String addBinary(String a, String b) {
        StringBuilder stringBuilder = new StringBuilder();
        int carry = 0;
        int i = a.length() - 1;
        int j = b.length() - 1;
        while(i >= 0 || j >= 0) {
            int sum = carry;
            if (i >= 0) {
                sum += a.charAt(i--) - '0';
            }
            if (j >= 0) {
                sum += b.charAt(j--) - '0';
            }
            stringBuilder.append(sum % 2);
            carry = sum / 2;
        }
        if (carry != 0) {
            stringBuilder.append(carry);
        }
        return stringBuilder.reverse().toString();
    }
    public static void main(String[] args) {
        String a = "11";
        String b = "1";
        System.out.println(addBinary(a, b));