[Leetcode P67]2진수 더하기

public class P67 {

    private static 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 (j >= 0){
            	sum += b.charAt(j--) - '0';
            }
            if (i >= 0){
            	sum += a.charAt(i--) - '0';
            }
            sb.append(sum % 2);
            carry = sum / 2;
        }
        
        if (carry != 0){
        	sb.append(carry);
        }
        
        return sb.reverse().toString();
    }

    public static void main(String[] args) {
        String s = addBinary("1001", "1001");
    }
}