Minimum Operations to Make the Array K-Increasing

class Solution {
public:
    int kIncreasing(vector<int>& arr, int k) {
        int lisLen=0;
        int n=arr.size();
        //LIS for K independent subarrays
        for(int i=0;i<k;++i){
            vector<int> lis;
            for(int j=i;j<n;j+=k){
                if(lis.empty() or lis.back()<=arr[j])
                    lis.push_back(arr[j]);
                else{
                    int ub = upper_bound(lis.begin(),lis.end(),arr[j])-lis.begin();
                    lis[ub] = arr[j];
                }
            }
            lisLen += lis.size();
        }
        return arr.size()-lisLen;
    }
};