leetcode67 二进制求和

给你两个二进制字符串 a 和 b ，以二进制字符串的形式返回它们的和。

示例 1：

输入:a = "11", b = "1"
输出："100"

示例 2：

输入：a = "1010", b = "1011"
输出："10101"

class Solution {
    public String addBinary(String a, String b) {
        if(a.length()==0) return b;
        if(b.length()==0) return a;
        String s = "";
        String ca = new StringBuffer(a).reverse().toString();
        String cb = new StringBuffer(b).reverse().toString();
        int t=0;
        int i=0;
        while (i<ca.length() && i<cb.length()){
            t += (ca.charAt(i)-'0') + (cb.charAt(i)-'0');
            s += Integer.toString(t%2);
            t=t/2;
            i++;
        }
        while (i<ca.length()){
            t += (ca.charAt(i)-'0');
            s += Integer.toString(t%2);
            t=t/2;
            i++;
        }
        while (i<cb.length()){
            t += (cb.charAt(i)-'0');
            s += Integer.toString(t%2);
            t=t/2;
            i++;
        }
        if(t!=0) s+='1';
        return new StringBuffer(s).reverse().toString();

    }
}