LeetCode - Add Binary

https://leetcode.com/problems/add-binary/

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

For example,
a = "11"
b = "1"
Return "100".

这道题就跟所有加法题一样，只要注意进位，和一个数加完后，处理另一个数剩余的位就行。

代码如下：

    public String addBinary(String a, String b) {
        char[] sa = a.toCharArray();
        char[] sb = b.toCharArray();
        
        int i=sa.length-1; 
        int j = sb.length-1;
        char[] longer = i>=j? sa:sb;
        int left = i>=j? i:j;
        int carry = 0;
        while(i>=0 && j>=0){
            int val = (sa[i]-'0') + (sb[j]-'0') + carry;
            longer[left] = (char)(val%2 + '0');
            carry = val/2;
            i--;
            j--;
            left--;
        }

        while(left>=0){
            int val = (longer[left]-'0') + carry;
            longer[left] = (char)(val%2 + '0');
            carry = val/2;
            left--;
        }
        String rst = new String(longer);
        if(carry>0) rst = "1" + rst;
        return rst;
    }