Add Binary leetcode

Add Binary

Apr 2 '12

5763 / 16556

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

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

我的丑陋的

public class Solution {    public String addBinary(String a, String b) {        if(a==null||b==null) return null;                int la = a.length(),lb = b.length();                int add = 0;        int i = la-1,j=lb-1;        StringBuilder sb = new StringBuilder();        while(i>=0 && j>=0){            int sum =( a.charAt(i)-'0')            +b.charAt(j)-'0'+add;                        add = sum/2;            sum = sum%2;            sb.insert(0,sum+"");            i--;            j--;        }        if(i>=0){            j=i;            b=a;        }                while(j>=0){            int sum = b.charAt(j)-'0'+add;  //            add = sum/2;            sum = sum%2;            sb.insert(0,sum+"");            j--;        }        if(add>0){            sb.insert(0,"1");  //        }        return sb.toString();    }}

别人的比较优美的写法

class Solution {public:    string addBinary(string a, string b) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        int la = a.size();        int lb = b.size();        string sum = la > lb ? a : b;        int overflow = 0;        for( int i = 0; i < sum.size(); i ++ )        {            char ca = i < la ? a[la - i - 1] : '0';            char cb = i < lb ? b[lb - i - 1] : '0';            int bit = ca - '0' + cb - '0' + overflow;            overflow = bit / 2;            sum[sum.size() - i - 1] = bit % 2 + '0';        }        if(overflow)        {            sum = "1" + sum;        }        return sum;    }};