题解 | #大数加法#

public String solve(String s, String t) {
        int slen = s.length() - 1;
        int tlen = t.length() - 1;
        int i;
        int j;
        int carry = 0;
        StringBuilder stringBuilder = new StringBuilder();

//从后往前依次进行加法操作
        while (slen >= 0 || tlen >= 0 || carry > 0) {
            if (slen < 0) {
                i = 0;
            } else {
                i = s.charAt(slen) - '0';
            }
            if (tlen < 0) {
                j = 0;
            } else {
                j = t.charAt(tlen) - '0';
            }
            slen--;
            tlen--;

            int sum = i + j + carry;//模拟进位
            stringBuilder.append(sum % 10);//只将与10的余数存储
            carry = sum / 10;//进位
        }

        return stringBuilder.reverse().toString();


    }