🚀 Minimum Operations to Make Array Values Equal to K

📘 Problem Statement

You are given an integer array nums and an integer k.

You can perform the following operation:

• Choose an integer h (called valid) such that all elements in nums that are strictly greater than h are equal.
• For each index i where nums[i] > h, set nums[i] = h.

Your goal is to make all values in nums equal to k using the minimum number of operations.
Return the minimum number of operations, or -1 if it's impossible.

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✅ What is a Valid h?

An integer h is valid if all values in nums that are strictly greater than h are equal.

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🧠 Examples

Example 1

Input: nums = [5, 2, 5, 4, 5], k = 2

Output: 2

Explanation:

• Operation 1: Choose h = 4 → nums becomes [4, 2, 4, 4, 4]

• Operation 2: Choose h = 2 → nums becomes [2, 2, 2, 2, 2]

Example 2

Input: nums = [2, 1, 2], k = 2

Output: -1

Explanation:

There's an element (1) smaller than k, so it's impossible.

Example 3

Input: nums = [9, 7, 5, 3], k = 1

Output: 4

Explanation:

• h = 7 → [7, 7, 5, 3]

• h = 5 → [5, 5, 5, 3]

• h = 3 → [3, 3, 3, 3]

• h = 1 → [1, 1, 1, 1]

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🧩 Constraints

• 1 <= nums.length <= 100
• 1 <= nums[i], k <= 100

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💡 Approach

1. Check for impossibility: If any element in nums is less than k, return -1 (since we can only decrease values).
2. Sort unique values in descending order.
3. Count valid operations from top down to k.

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🧪 Python Code

class Solution:
    def minOperations(self, nums, k):
        if any(num < k for num in nums):
            return -1

        from collections import Counter

        freq = Counter(nums)
        unique_values = sorted(freq.keys(), reverse=True)

        operations = 0
        i = 0

        while i < len(unique_values) and unique_values[i] > k:
            operations += 1
            i += 1

        return operations