Add Binary

Add Binary

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) {
        char num1[] = a.toCharArray();
        char num2[] = b.toCharArray();
        int result[] = new int[Math.max(a.length(), b.length()) + 1];//保存结果
        int i = num1.length - 1;
        int j = num2.length - 1;
        int k = result.length - 1;
        while(i >= 0 && j >= 0){
            if(num1[i] == '1' && num2[j] == '1')
                result[k--] = 2;
            else if(num1[i] == '0' && num2[j] == '0')
                result[k--] = 0;
            else
                result[k--] = 1;
            i--;
            j--;
        }//至少有一个计算完成
        while(i >= 0){
            result[k--] = num1[i--] - '0';
        }
        while(j >= 0)
            result[k--] = num2[j--] - '0';
        k = result.length - 1;
        while(k > 0){
            if(result[k] / 2 == 1)
            {
                result[k - 1] += 1;
                result[k] %= 2;
            }
            k--;
        }
        String ret = "";
        if(result[0] != 0){
            for(i = 0; i < result.length; i++)
                ret += String .valueOf(result[i]);
        }
        else
        {
            for(i = 1; i < result.length; i++)
                ret += String .valueOf(result[i]);
        }
        return ret;
    }
}