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2712. Minimum Cost to Make All Characters Equal 👍

  • Time: $O(n)$
  • Space: $O(1)$
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class Solution {
 public:
  long long minimumCost(string s) {
    const int n = s.length();
    long long ans = 0;

    for (int i = 1; i < n; ++i)
      if (s[i] != s[i - 1])
        // Invert s[0..i - 1] or s[i..n - 1].
        ans += min(i, n - i);

    return ans;
  }
};

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class Solution {
  public long minimumCost(String s) {
    final int n = s.length();
    long ans = 0;

    for (int i = 1; i < n; ++i)
      if (s.charAt(i) != s.charAt(i - 1))
        // Invert s[0..i - 1] or s[i..n - 1].
        ans += Math.min(i, n - i);

    return ans;
  }
}

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class Solution:
  def minimumCost(self, s: str) -> int:
    n = len(s)
    ans = 0

    for i in range(1, n):
      if s[i] != s[i - 1]:
        # Invert s[0..i - 1] or s[i..n - 1].
        ans += min(i, n - i)

    return ans