_LeetCode-67Add Binary

 Add Binary

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

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

求两个二进制数的和

java代码:

public class Solution {
    public String addBinary(String a, String b) {
        StringBuilder sb=new StringBuilder();
        int i=a.length()-1;
        int j=b.length()-1;
        int carry=0;
        while(i>=0||j>=0){
            int sum=carry;
            if(i>=0)sum+=a.charAt(i--)-'0';
            if(j>=0)sum+=b.charAt(j--)-'0';
            sb.append(sum%2);
            carry=sum/2;
        }
        if(carry!=0)sb.append(carry);
        return sb.reverse().toString();
    }
}