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1432. Max Difference You Can Get From Changing an Integer 👎

  • Time: $O(\log \texttt{num})$
  • Space: $O(\log \texttt{num})$
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class Solution {
 public:
  int maxDiff(int num) {
    const string s = to_string(num);
    int firstNot9 = s.find_first_not_of('9');
    int firstNot01 = s.find_first_not_of("01");
    if (firstNot9 == string::npos)
      firstNot9 = 0;
    if (firstNot01 == string::npos)
      firstNot01 = 0;

    string a = s;
    string b = s;
    replace(a.begin(), a.end(), s[firstNot9], '9');
    replace(b.begin(), b.end(), s[firstNot01], firstNot01 == 0 ? '1' : '0');
    return stoi(a) - stoi(b);
  }
};

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class Solution {
  public int maxDiff(int num) {
    final String s = String.valueOf(num);
    final int firstNot9 = firstNot(s, '9', '9');
    final int firstNot01 = firstNot(s, '0', '1');
    final String a = s.replace(s.charAt(firstNot9), '9');
    final String b = s.replace(s.charAt(firstNot01), firstNot01 == 0 ? '1' : '0');
    return Integer.parseInt(a) - Integer.parseInt(b);
  }

  private int firstNot(final String s, char a, char b) {
    for (int i = 0; i < s.length(); ++i)
      if (s.charAt(i) != a && s.charAt(i) != b)
        return i;
    return 0;
  }
}

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class Solution:
  def maxDiff(self, num: int) -> int:
    s = str(num)

    def firstNot(s: str, t: str) -> int:
      for i, c in enumerate(s):
        if all(c != d for d in t):
          return i
      return 0

    firstNot9 = firstNot(s, '9')
    firstNot01 = firstNot(s, '01')
    a = s.replace(s[firstNot9], '9')
    b = s.replace(s[firstNot01], '1' if firstNot01 == 0 else '0')
    return int(a) - int(b)