跟你的差不多，短的字符串前边先补0 public String solve (String s, String t) { // write code here if (s.isEmpty()) { return t; } if (t.isEmpty()) { return s; } String longStr; String shortStr; if (s.length() >= t.length()) { longStr = s; shortStr = t; } else { longStr = t; shortStr = s; } StringBuilder sb = new StringBuilder(); for (int i = 0; i < longStr.length() - shortStr.length(); i++) { sb.append("0"); } shortStr = sb.append(shortStr).toString(); StringBuilder result = new StringBuilder(); int carry = 0; for (int i = longStr.length() - 1, j = shortStr.length() - 1; i >= 0; i--, j--) { int sum = longStr.charAt(i) - '0' + shortStr.charAt(i) - '0' + carry; if (sum > 9) { carry = 1; sum = sum - 10; } else { carry = 0; } result.insert(0, sum); } if (carry == 1) { result.insert(0, 1); } return result.toString(); } }