67. Add Binary

67. Add Binary

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

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

class Solution {    public String addBinary(String a, String b) {        int x=BinaryToDecimal(a);        int y=BinaryToDecimal(b);        return Integer.toBinaryString(x+y);        }    public int BinaryToDecimal(String s){        char[] chars=s.toCharArray();        int length=s.length();        int result = 0;        for(int i=0;i<length;i++){            result+=(chars[i]-48)*Math.pow(2, length-i-1);        }        return result;    }}

二进制过长，如111111111111000001101010，则超过运算限制。

improve:

public class AddBinary {    public String addBinary(String a, String b) {               char[] ca=a.toCharArray();        char[] cb=b.toCharArray();        int la=a.length()-1;        int lb=b.length()-1;        int add=0;        StringBuilder sb=new StringBuilder();        while(la>=0||lb>=0||add==1){            //从最小为开始，进行每次运算            int ta= (la)<0? 0:ca[la--] -'0';            int tb= (lb)<0? 0:cb[lb--] -'0';            //取余为新位            sb.insert(0, (ta+tb+add)%2);            add=(ta+tb+add)/2;        }        return sb.toString();        }}