2914. Minimum Number of Changes to Make Binary String Beautiful

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String Greedy

Time: O(n)

Space: O(1)

Intuition

Minimum string changes to make string good (each character has even count). Count characters with odd frequency.

Algorithm

1Count frequencies. Odd frequency chars must pair up. Min changes = oddCount / 2.

Common Pitfalls

•Each swap can fix two odd-frequency characters. Minimum changes = floor(oddCount/2).

2914.cs

// Approach: Scan even-indexed pairs; each mismatched pair costs 1 change.
// Time: O(n) Space: O(1)

public class Solution
{
    public int MinChanges(string s)
    {
        int ans = 0;

        for (int i = 0; i + 1 < s.Length; i += 2)
        {
            if (s[i] != s[i + 1])
                ++ans;
        }

        return ans;
    }
}

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