leetcode Add Binary

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

For example,
a = "11"
b = "1"

Return "100".

题目本身还是比较简单的，就是二进制加法，不过写程序的时候发现自己对字符串的api还是有点生疏，贴出来以便复习用吧~注意一下进位的取值就可以了。

public String addBinary(String a, String b) {    String res=new String();    int exceed = 0;    int bits=0;    int indexa = a.length() - 1, indexb = b.length() - 1;    while (indexa >= 0 && indexb >= 0) {        int result = a.charAt(indexa)-'0'+b.charAt(indexb)-'0'+exceed;        bits=result%2;        exceed=result/2;        res=""+bits+""+res;        indexa--;        indexb--;    }    while(indexa>=0) {        int result = exceed + a.charAt(indexa)-'0';        bits=result%2;        exceed=result/2;        res=""+bits+""+res;        indexa--;    }    while(indexb>=0) {        int result = exceed + b.charAt(indexb)-'0';        bits=result%2;        exceed=result/2;        res=""+bits+""+res;        indexb--;    }    if(exceed==1)        res=""+exceed+""+res;    StringBuffer str=new StringBuffer();    return res;}