Frequencies of Limited Range Array Elements

class Solution{
    public:
    //Function to count the frequency of all elements from 1 to N in the array.
    void frequencyCount(vector<int>& arr,int N, int P)
    { 
        // code here
        
        
        P++;
        
        for (int i = 0; i < N; i++) 
        {
            int index = (arr[i] % P) - 1;
            
            if (index >= 0 && index < N) 
            {
                
                arr[index] += P;
            }
        }

        for (int i = 0; i < N; i++) 
        {
            
            arr[i] = arr[i] / P;
            
        }
        
        
        
        
    }
};