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2417. Closest Fair Integer

  • Time: $O(1)$
  • Space: $O(1)$
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class Solution {
 public:
  int closestFair(int n) {
    const int digitsCount = to_string(n).length();
    return (digitsCount & 1) ? getOddDigits(digitsCount) : getEvenDigits(n);
  }

 private:
  long getOddDigits(int digitsCount) {
    const int zerosCount = (digitsCount + 1) / 2;
    const int onesCount = (digitsCount - 1) / 2;
    return stoi('1' + string(zerosCount, '0') + string(onesCount, '1'));
  }

  int getEvenDigits(int n) {
    const int digitsCount = to_string(n).length();
    const long maxNum = stol('1' + string(digitsCount, '0'));
    for (long num = n; num < maxNum; ++num)
      if (isValidNum(num))
        return num;
    return getOddDigits(digitsCount + 1);
  }

  bool isValidNum(long num) {
    int count = 0;
    const string s = to_string(num);
    for (const char c : s)
      count += (c - '0' & 1) ? -1 : 1;
    return count == 0;
  }
};

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class Solution {
  public int closestFair(int n) {
    final int digitsCount = String.valueOf(n).length();
    return (digitsCount % 2 == 1) ? (int) getOddDigits(digitsCount) : getEvenDigits(n);
  }

  private long getOddDigits(int digitsCount) {
    final int zerosCount = (digitsCount + 1) / 2;
    final int onesCount = (digitsCount - 1) / 2;
    return Integer.valueOf('1' + "0".repeat(zerosCount) + "1".repeat(onesCount));
  }

  private int getEvenDigits(int n) {
    final int digitsCount = String.valueOf(n).length();
    final long maxNum = Long.valueOf('1' + "0".repeat(digitsCount));
    for (long num = n; num < maxNum; ++num)
      if (isValidNum(num))
        return (int) num;
    return (int) getOddDigits(digitsCount + 1);
  }

  private boolean isValidNum(long num) {
    int count = 0;
    for (final char c : String.valueOf(num).toCharArray())
      count += ((c - '0') % 2 == 1) ? -1 : 1;
    return count == 0;
  }
}

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class Solution:
  def closestFair(self, n: int) -> int:
    digitsCount = len(str(n))
    return self._getOddDigits(digitsCount) if digitsCount & 1 else self._getEvenDigits(n)

  def _getOddDigits(self, digitsCount: int) -> int:
    zerosCount = (digitsCount + 1) // 2
    onesCount = (digitsCount - 1) // 2
    return '1' + '0' * zerosCount + '1' * onesCount

  def _getEvenDigits(self, n: int) -> int:
    digitsCount = len(str(n))
    maxNum = int('1' + '0' * digitsCount)
    for num in range(n, maxNum):
      if self._isValidNum(num):
        return num
    return self._getOddDigits(digitsCount + 1)

  def _isValidNum(self, num: int) -> bool:
    count = 0
    s = str(num)
    for c in s:
      count += -1 if ord(c) - ord('0') & 1 else 1
    return count == 0