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3019. Number of Changing Keys 👍

  • Time: $O(n)$
  • Space: $O(1)$
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class Solution {
 public:
  int countKeyChanges(string s) {
    int ans = 0;
    for (int i = 1; i < s.length(); ++i)
      if (tolower(s[i]) != tolower(s[i - 1]))
        ++ans;
    return ans;
  }
};

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class Solution {
  public int countKeyChanges(String s) {
    int ans = 0;
    for (int i = 1; i < s.length(); ++i)
      if (Character.toLowerCase(s.charAt(i)) != Character.toLowerCase(s.charAt(i - 1)))
        ++ans;
    return ans;
  }
}

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class Solution:
  def countKeyChanges(self, s: str) -> int:
    return sum(a.lower() != b.lower()
               for a, b in itertools.pairwise(s))