LeetCode 3137: Minimum Number of Operations to Make Word K-Periodic Solution

Master LeetCode problem 3137 (Minimum Number of Operations to Make Word K-Periodic), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

3137. Minimum Number of Operations to Make Word K-Periodic

Medium

Hash Table String Counting

Problem Explanation

Explanation:

To solve this problem, we can iterate through all possible choices of i and j such that they are divisible by k. For each pair of i and j, we can calculate the number of operations required to make the word k-periodic by replacing the substring at index i with the substring at index j.

We can achieve this by checking the characters at indices i and j for equality and counting how many characters need to be replaced. The minimum number of operations will be the minimum count obtained over all pairs of i and j.

Algorithm:

Iterate through all possible pairs of i and j such that i and j are divisible by k.
For each pair, calculate the count of characters that need to be replaced.
Keep track of the minimum count obtained.
Return the minimum count as the answer.

Time Complexity:

The time complexity of this algorithm is O(n) where n is the length of the input word.

Space Complexity:

The space complexity of this algorithm is O(1) as we are not using any extra space apart from some constant extra space.

Solution Code

class Solution {
    public int minChanges(String word, int k) {
        int n = word.length();
        int minChanges = Integer.MAX_VALUE;
        
        for (int i = 0; i < k; i++) {
            int changes = 0;
            for (int j = i; j < n; j += k) {
                if (word.charAt(j) != word.charAt(i)) {
                    changes++;
                }
            }
            minChanges = Math.min(minChanges, changes);
        }
        
        return minChanges;
    }
}

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