3375. Minimum Operations to Make Array Values Equal to K

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

An integer h is called valid if all values in the array that are strictly greater than h are identical.

For example, if nums = [10, 8, 10, 8], a valid integer is h = 9 because all nums[i] > 9 are equal to 10, but 5 is not a valid integer.

You are allowed to perform the following operation on nums:

• Select an integer h that is valid for the current values in nums.
• For each index i where nums[i] > h, set nums[i] to h.

Return the minimum number of operations required to make every element in nums equal to k. If it is impossible to make all elements equal to k, return -1.

class Solution {
public:
    int minOperations(vector<int>& nums, int k) {
        sort(begin(nums), end(nums));
        if (nums[0] < k) return -1;
        int res = 0;
        while(nums.size() and nums.back() > k) {
            int x = nums.back(); 
            res++;
            while(nums.size() and nums.back() == x) nums.pop_back();
        }
        return res;
    }
};