leetcode

0 class Solution {

1 long long generate(long long left, bool isEvenn) const {

2 long long palindrome = left;

3 if (!isEvenn) left /= 10;

4 while (left > 0) {

5 palindrome = palindrome * 10 + left % 10;

6 left /= 10;

7 }

8 return palindrome;

9 }

10

11 public:

12 string nearestPalindromic(const string &s) const {

13 if (s == "999999999999999999") return "1000000000000000001";

14

15 const long long number = stoll(s);

16 if (number <= 10) return to_string(number - 1);

17 if (number == 11) return "9";

18

19 const int n = size(s);

20 const long long left = stoll(s.substr(0, (n + 1) / 2));

21

22 long long vec[5] = {generate(left - 1, n % 2 == 0), generate(left, n % 2 == 0),

23 (long long)pow(10, n - 1) - 1, (long long)pow(10, n) + 1,

24 left < 999999999 ? generate(left + 1, n % 2 == 0)

25 : stoll("1" + string(n - 1, '0') + "1")};

26

27 long long res = 0, mini = LLONG_MAX;

28 for (const auto crnt : vec) {

29 if (crnt == number) continue;

30

31 const auto diff = abs(crnt - number);

32 if (diff < mini || (diff == mini && crnt < res)) {

33 mini = diff;

34 res = crnt;

35 }

36 }

37

38 return to_string(res);

39 }

40 };