[LeetCode] Add Binary

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

For example,

a = 

"11"

b = 

"1"

Return 

"100"

.

public class Solution {
public String addBinary(String a, String b) {
int carry = 0;
int sum = 0;
StringBuilder result = new StringBuilder();
int i;

for (i = 0; i < a.length() && i < b.length(); i++) {
int m = a.charAt(a.length() - i - 1) - '0';
int n = b.charAt(b.length() - i - 1) - '0';

sum = (carry + m + n) % 2;
carry = (carry + m + n) / 2;

result.insert(0, sum + "");
}

for (; i < a.length(); i++) {
int m = a.charAt(a.length() - i - 1) - '0';

sum = (carry + m) % 2;
carry = (carry + m) / 2;

result.insert(0, sum + "");
}

for (; i < b.length(); i++) {
int m = b.charAt(b.length() - i - 1) - '0';

sum = (carry + m) % 2;
carry = (carry + m) / 2;

result.insert(0, sum + "");
}

if (carry == 1) {
result.insert(0, carry + "");
}

return result.toString();
}
}