Maximum litres of water that can be bought with N Rupees

Given Rupees. A liter plastic bottle of water costs Rupees and a litre of glass bottle of water costs Rupees. But the empty glass bottle after buying can be exchanged for Rupees. Find the maximum liters of water which can be bought with Rupees.

Examples: 

Input: N = 10 , A = 11 , B = 9 , C = 8 
Output:
One glass bottle can be bought and then can be returned to buy one more glass bottle

Input: N = 15 , A = 6 , B = 4 , C = 3 
Output: 12 

Approach: If we have at least money then cost of one glass bottle is b – c. This means that if a ? (b – c) then we don’t need to buy glass bottles, only plastic ones, and the answer will be floor(n / a). Otherwise we need to buy glass bottles while we can. 

So, if we have at least money, then we will buy floor((n – c) / (b – c)) glass bottles and then spend rest of the money on plastic ones.

Below is the implementation of the above approach: 

C++

// CPP implementation of the above approach
#include<bits/stdc++.h>
using namespace std;
 
 
void maxLitres(int budget,int plastic,int glass,int refund)
{
 
    // if buying glass bottles is profitable
    if (glass - refund < plastic)
       {
           // Glass bottles that can be bought
        int ans = max((budget - refund) / (glass - refund), 0);
 
        // Change budget according the bought bottles
        budget -= ans * (glass - refund);
 
        // Plastic bottles that can be bought
        ans += budget / plastic;
        cout<<ans<<endl;
       }
 
    // if only plastic bottles need to be bought
    else
        cout<<(budget / plastic)<<endl;
}
 
     
 
// Driver Code
int main()
{
    int budget = 10, plastic=11, glass=9, refund =  8;
    maxLitres(budget, plastic, glass, refund);
}
 
// This code is contributed by
// Surendra_Gangwar

                    

Java

// Java implementation of the above approach
class GFG
{
 
    static void maxLitres(int budget, int plastic,
                            int glass, int refund)
    {
 
        // if buying glass bottles is profitable
        if (glass - refund < plastic)
        {
             
            // Glass bottles that can be bought
            int ans = Math.max((budget - refund) / (glass - refund), 0);
 
            // Change budget according the bought bottles
            budget -= ans * (glass - refund);
 
            // Plastic bottles that can be bought
            ans += budget / plastic;
            System.out.println(ans);
        }
         
        // if only plastic bottles need to be bought
        else
        {
            System.out.println((budget / plastic));
        }
 
    }
 
    // Driver Code
    public static void main(String[] args)
    {
        int budget = 10, plastic = 11, glass = 9, refund = 8;
        maxLitres(budget, plastic, glass, refund);
    }
}
 
/* This code contributed by PrinciRaj1992 */

                    

Python3

# Python3 implementation of the above approach
 
def maxLitres(budget, plastic, glass, refund):
 
    # if buying glass bottles is profitable
    if glass - refund < plastic:
 
        # Glass bottles that can be bought
        ans = max((budget - refund) // (glass - refund), 0)
 
        # Change budget according the bought bottles
        budget -= ans * (glass - refund)
 
        # Plastic bottles that can be bought
        ans += budget // plastic
        print(ans)
 
    # if only plastic bottles need to be bought
    else:
        print(budget // plastic)
 
# Driver Code
budget, plastic, glass, refund = 10, 11, 9, 8
maxLitres(budget, plastic, glass, refund)

                    

C#

// C# implementation of the above approach
using System;   
 
class GFG
{
 
    static void maxLitres(int budget, int plastic,
                            int glass, int refund)
    {
 
        // if buying glass bottles is profitable
        if (glass - refund < plastic)
        {
             
            // Glass bottles that can be bought
            int ans = Math.Max((budget - refund) / (glass - refund), 0);
 
            // Change budget according the bought bottles
            budget -= ans * (glass - refund);
 
            // Plastic bottles that can be bought
            ans += budget / plastic;
            Console.WriteLine(ans);
        }
         
        // if only plastic bottles need to be bought
        else
        {
            Console.WriteLine((budget / plastic));
        }
 
    }
 
    // Driver Code
    public static void Main(String[] args)
    {
        int budget = 10, plastic = 11, glass = 9, refund = 8;
        maxLitres(budget, plastic, glass, refund);
    }
}
 
// This code contributed by Rajput-Ji

                    

PHP

<?php
// PHP implementation of the above approach
 
function maxLitres($budget, $plastic,
                   $glass, $refund)
{
 
    // if buying glass bottles is profitable
    if ($glass - $refund < $plastic)
    {
        // Glass bottles that can be bought
        $ans = max((int)($budget - $refund) /
                        ($glass - $refund), 0);
 
        // Change budget according the bought bottles
        $budget -= $ans * ($glass - $refund);
 
        // Plastic bottles that can be bought
        $ans += (int)($budget / $plastic);
        echo $ans . "\n";
    }
 
    // if only plastic bottles need to be bought
    else
        echo (int)($budget / $plastic) . "\n";
}
 
// Driver Code
$budget = 10;
$plastic = 11;
$glass = 9;
$refund = 8;
maxLitres($budget, $plastic,
          $glass, $refund);
 
// This code is contributed by mits
?>

                    

Javascript

<script>
 
// Javascript implementation of the above approach
 
    function maxLitres(budget, plastic,
                            glass, refund)
    {
   
        // if buying glass bottles is profitable
        if (glass - refund < plastic)
        {
               
            // Glass bottles that can be bought
            let ans = Math.max((budget - refund) / (glass - refund), 0);
   
            // Change budget according the bought bottles
            budget -= ans * (glass - refund);
   
            // Plastic bottles that can be bought
            ans += Math.floor(budget / plastic);
            document.write(ans);
        }
           
        // if only plastic bottles need to be bought
        else
        {
            document.write(Math.floor(budget / plastic));
        }
   
    }
     
    // Driver code
 
    let budget = 10, plastic = 11, glass = 9, refund = 8;
    maxLitres(budget, plastic, glass, refund);
       
</script>

                    

Output
2

Time complexity: O(1)
Auxiliary space: O(1)