题解 | #大数加法#

public String solve (String s, String t) {
        int sLen = s.length() - 1, tLen = t.length() - 1, carry = 0;
        StringBuilder result = new StringBuilder();
        while(sLen >= 0 || tLen >= 0 || carry > 0){
            int sNum = sLen >= 0 ? s.charAt(sLen --) - '0' : 0;
            int tNum = tLen >= 0 ? t.charAt(tLen --) - '0' : 0;
            int sum = sNum + tNum + carry;
            result.append(sum % 10);
            carry = sum / 10;
        }
        return result.reverse().toString();
    }