Capacity To Ship Packages Within D Days

class Solution {
  public:
   bool ispossible(int mid , int arr[] , int d, int n) 
    {
        bool check = true ; 
        int s = 0 ;
        d-- ;
        for(int i = 0 ; i < n ; i++ )
        {
            if(arr[i] > mid)
            {
                return false ; 
            }
            else if(s + arr[i] <= mid)
            {
                s = s + arr[i] ; 
            }
            else
            {
               s = arr[i] ; 
               d-- ; 
            }
        }
        return d >= 0 ;
    }
    int leastWeightCapacity(int arr[], int N, int D) {
        // code here
        int l =  1 ; 
        int w = 0 ; 
        
        for(int i = 0 ; i < N ; i++) {
            w  = w + arr[i] ;
          }
         // cout << w << endl ; 
          int r = w ;
          
        int mid ;
        while(l <= r)
        {
             mid =( l + r) / 2 ; 
            if(ispossible(mid ,arr , D , N))
            {
             // cout << mid << endl ;
              r = mid - 1 ; 
                
            }
            else
            {
                l = mid + 1 ; 
            }
        }
        return l ; 
    }
};