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906. Super Palindromes 👎

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class Solution {
 public:
  int superpalindromesInRange(string left, string right) {
    int ans = 0;
    const long l = stoll(left);
    const long r = stoll(right);

    for (long i = sqrt(l); i * i <= r;) {
      const long palindrome = nextPalindrome(i);
      const long squared = palindrome * palindrome;
      if (squared <= r && isPalindrome(squared))
        ++ans;
      i = palindrome + 1;
    }

    return ans;
  }

 private:
  long nextPalindrome(int num) {
    const string s = to_string(num);
    const int n = s.length();
    string half = s.substr(0, (n + 1) / 2);
    string reversedHalf = reversed(half.substr(0, n / 2));
    const long candidate = stoll(half + reversedHalf);
    if (candidate >= num)
      return candidate;
    half = to_string(stoll(half) + 1);
    reversedHalf = reversed(half.substr(0, n / 2));
    return stoll(half + reversedHalf);
  }

  string reversed(const string& s) {
    return {s.rbegin(), s.rend()};
  }

  bool isPalindrome(long num) {
    const string s = to_string(num);
    int l = 0;
    int r = s.length() - 1;
    while (l < r)
      if (s[l++] != s[r--])
        return false;
    return true;
  }
};

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class Solution {
  public int superpalindromesInRange(String left, String right) {
    int ans = 0;
    Long l = Long.valueOf(left);
    Long r = Long.valueOf(right);

    for (long i = (long) Math.sqrt(l); i * i <= r;) {
      long palindrome = nextPalindrome(i);
      long squared = palindrome * palindrome;
      if (squared <= r && isPalindrome(squared))
        ++ans;
      i = palindrome + 1;
    }

    return ans;
  }

  private long nextPalindrome(long num) {
    final String s = String.valueOf(num);
    final int n = s.length();

    String half = s.substring(0, (n + 1) / 2);
    String reversedHalf = new StringBuilder(half.substring(0, n / 2)).reverse().toString();
    final long candidate = Long.valueOf(half + reversedHalf);
    if (candidate >= num)
      return candidate;

    half = String.valueOf(Long.valueOf(half) + 1);
    reversedHalf = new StringBuilder(half.substring(0, n / 2)).reverse().toString();
    return Long.valueOf(half + reversedHalf);
  }

  private boolean isPalindrome(long num) {
    final String s = String.valueOf(num);
    int l = 0;
    int r = s.length() - 1;

    while (l < r)
      if (s.charAt(l++) != s.charAt(r--))
        return false;

    return true;
  }
}

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class Solution:
  def superpalindromesInRange(self, left: str, right: str) -> int:
    def nextPalindrome(num: int) -> int:
      s = str(num)
      n = len(s)

      half = s[0:(n + 1) // 2]
      reversedHalf = half[:n // 2][::-1]
      candidate = int(half + reversedHalf)
      if candidate >= num:
        return candidate

      half = str(int(half) + 1)
      reversedHalf = half[:n // 2][::-1]
      return int(half + reversedHalf)

    def isPalindrome(num: int) -> bool:
      s = str(num)
      l = 0
      r = len(s) - 1

      while l < r:
        if s[l] != s[r]:
          return False
        l += 1
        r -= 1

      return True

    ans = 0
    l = int(left)
    r = int(right)
    i = math.isqrt(l)

    while i * i <= r:
      palindrome = nextPalindrome(i)
      squared = palindrome**2
      if squared <= r and isPalindrome(squared):
        ans += 1
      i = palindrome + 1

    return ans