67. Add Binary

题目

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

For example,

a = "11"

b = "1"

Return "100".

我的解法

public class Solution {
    public String addBinary(String a, String b) {
        StringBuilder sb = new StringBuilder();
        int i = 0;
        int mark = 0;
        while(i < a.length() || i < b.length()){
            int x = (a.length() > i) ? a.charAt(a.length() - 1 - i) - '0': 0;
            int y = (b.length() > i) ? b.charAt(b.length() - 1 - i) - '0': 0;
            sb.append((x + y + mark)%2);
            mark = (x + y + mark)/2;
            i++;
        }
        if(mark == 1)
            return sb.append(mark).reverse().toString();
        return sb.reverse().toString();
    }
}

算法分析：注意红色标记地方，要用字符-‘0’，才得到对应数字的值。