Check if X can give change to every person in the Queue

Last Updated : 15 Jul, 2022

Given an array of N integers where A_i denotes the currency of note that the i-th person has. The possible currencies are 5, 10, and 20. All the N people are standing in a queue waiting to buy an ice cream from X which costs Rs 5. Initially, X has an initial balance of 0. Check if X will be able to provide change for all people who are waiting to buy ice cream.

Examples:

Input:a[] = {5, 5, 5, 10, 20}
Output: YES
When the fourth person comes to buy an ice-cream, X has three Rs 5
change, hence X gives him 1, and now when the fifth person
comes to buy the ice-cream, X has two Rs 5 and one Rs 10 note, hence he
gives him one Rs 10 and one Rs 5 note.

Input: a[] = {5, 10, 10, 20}
Output: NO

The approach is to keep track of the number of Rs 5 and Rs 10 currencies. Rs 20 currencies will not be used since it is the highest currency that a person can give and thus it cannot be given as a change. Initialize two variables to count Rs 5(fiveCount) and Rs 10(tenCount). If the person has a Rs 10 currency and fiveCount > 0, then decrease fiveCount and increase tenCount. If X does not have Rs 5, then X cannot give the person the required change. If the person has 5$ note, increase fiveCount by one. If the person has Rs 20, then three conditions will be:

If fiveCount > 0 and tencount > 0, decrease both.
Else if, fiveCount >= 3, decrease fivecount by three.
Else, return false.

If all the person in the queue gets the change, then print "YES" else print "NO".

Below is the implementation of the above idea.

C++

// C++ program to check whether X can give change
// to every person in the Queue
#include <bits/stdc++.h>
using namespace std;

// Function to check if every person will
// get the change from X
int isChangeable(int notes[], int n)
{
    // To count the 5$ and 10& notes
    int fiveCount = 0;
    int tenCount = 0;

    // Serve the customer in order
    for (int i = 0; i < n; i++) {

        // Increase the number of 5$ note by one
        if (notes[i] == 5)
            fiveCount++;
        else if (notes[i] == 10) {

            // decrease the number of note 5$ and
            // increase 10$ note by one
            if (fiveCount > 0) {
                fiveCount--;
                tenCount++;
            }
            else
                return 0;
        }
        else {

            // decrease 5$ and 10$ note by one
            if (fiveCount > 0 && tenCount > 0) {
                fiveCount--;
                tenCount--;
            }

            // decrease 5$ note by three
            else if (fiveCount >= 3) {
                fiveCount -= 3;
            }
            else
                return 0;
        }
    }

    return 1;
}
// Driver Code
int main()
{
    // queue of customers with available notes.
    int a[] = { 5, 5, 5, 10, 20 };
    int n = sizeof(a) / sizeof(a[0]);

    // Calling function
    if (isChangeable(a, n))
        cout << "YES";
    else
        cout << "NO";

    return 0;
}

Java

// Java program to check 
// whether X can give 
// change to every person 
// in the Queue
import java.io.*;

class GFG 
{
    
// Function to check if
// every person will
// get the change from X
static int isChangeable(int notes[], 
                        int n)
{
    // To count the 5$
    // and 10& notes
    int fiveCount = 0;
    int tenCount = 0;

    // Serve the customer 
    // in order
    for (int i = 0; i < n; i++) 
    {

        // Increase the number
        // of 5$ note by one
        if (notes[i] == 5)
            fiveCount++;
        else if (notes[i] == 10) 
        {

            // decrease the number 
            // of note 5$ and 
            // increase 10$ note by one
            if (fiveCount > 0) 
            {
                fiveCount--;
                tenCount++;
            }
            else
                return 0;
        }
        else 
        {

            // decrease 5$ and 
            // 10$ note by one
            if (fiveCount > 0 && 
                tenCount > 0) 
            {
                fiveCount--;
                tenCount--;
            }

            // decrease 5$ 
            // note by three
            else if (fiveCount >= 3) 
            {
                fiveCount -= 3;
            }
            else
                return 0;
        }
    }

    return 1;
}

// Driver Code
public static void main (String[] args) 
{
    
// queue of customers 
// with available notes.
int a[] = {5, 5, 5, 10, 20};
int n = a.length;

// Calling function
if (isChangeable(a, n) > 0)
    System.out.print("YES");
else
    System.out.print("NO");
}
}

// This code is contributed 
// by anuj_67.

Python3

# Python program to check whether X can 
# give change to every person in the Queue

# Function to check if every person 
# will get the change from X
def isChangeable(notes, n):
    
    # To count the 5$ and 10& notes
    fiveCount = 0
    tenCount = 0
    
    # Serve the customer in order
    for i in range(n):
        
        # Increase the number of 5$ note by one
        if (notes[i] == 5):
            fiveCount += 1
        elif(notes[i] == 10):
            
            # decrease the number of note 5$ 
            # and increase 10$ note by one
            if (fiveCount > 0):
                fiveCount -= 1
                tenCount += 1
            else:
                return 0
        else:
            
            # decrease 5$ and 10$ note by one
            if (fiveCount > 0 and tenCount > 0):
                fiveCount -= 1
                tenCount -= 1
                
            # decrease 5$ note by three
            elif (fiveCount >= 3):
                fiveCount -= 3
            else:
                return 0
    return 1

# Driver Code

# queue of customers with available notes.
a = [5, 5, 5, 10, 20 ]
n = len(a)

# Calling function
if (isChangeable(a, n)):
    print("YES")
else:
    print("NO")

# This code is contributed by PrinciRaj1992

// C# program to check 
// whether X can give 
// change to every person 
// in the Queue
using System;

class GFG 
{
    
// Function to check if
// every person will
// get the change from X
static int isChangeable(int []notes, 
                        int n)
{
    // To count the 5$
    // and 10& notes
    int fiveCount = 0;
    int tenCount = 0;

    // Serve the customer 
    // in order
    for (int i = 0; i < n; i++) 
    {

        // Increase the number
        // of 5$ note by one
        if (notes[i] == 5)
            fiveCount++;
        else if (notes[i] == 10) 
        {

            // decrease the number 
            // of note 5$ and 
            // increase 10$ note by one
            if (fiveCount > 0) 
            {
                fiveCount--;
                tenCount++;
            }
            else
                return 0;
        }
        else
        {

            // decrease 5$ and 
            // 10$ note by one
            if (fiveCount > 0 && 
                tenCount > 0) 
            {
                fiveCount--;
                tenCount--;
            }

            // decrease 5$ 
            // note by three
            else if (fiveCount >= 3) 
            {
                fiveCount -= 3;
            }
            else
                return 0;
        }
    }

    return 1;
}

// Driver Code
public static void Main () 
{
    
// queue of customers 
// with available notes.
int []a = {5, 5, 5, 10, 20};
int n = a.Length;

// Calling function
if (isChangeable(a, n) > 0)
    Console.WriteLine("YES");
else
    Console.WriteLine("NO");
}
}

// This code is contributed 
// by anuj_67.

JavaScript

<script>
    // Javascript program to check 
    // whether X can give 
    // change to every person 
    // in the Queue
    
    // Function to check if
    // every person will
    // get the change from X
    function isChangeable(notes, n)
    {
        // To count the 5$
        // and 10& notes
        let fiveCount = 0;
        let tenCount = 0;

        // Serve the customer 
        // in order
        for (let i = 0; i < n; i++) 
        {

            // Increase the number
            // of 5$ note by one
            if (notes[i] == 5)
                fiveCount++;
            else if (notes[i] == 10) 
            {

                // decrease the number 
                // of note 5$ and 
                // increase 10$ note by one
                if (fiveCount > 0) 
                {
                    fiveCount--;
                    tenCount++;
                }
                else
                    return 0;
            }
            else
            {

                // decrease 5$ and 
                // 10$ note by one
                if (fiveCount > 0 && 
                    tenCount > 0) 
                {
                    fiveCount--;
                    tenCount--;
                }

                // decrease 5$ 
                // note by three
                else if (fiveCount >= 3) 
                {
                    fiveCount -= 3;
                }
                else
                    return 0;
            }
        }

        return 1;
    }
    
    // queue of customers 
    // with available notes.
    let a = [5, 5, 5, 10, 20];
    let n = a.length;

    // Calling function
    if (isChangeable(a, n) > 0)
        document.write("YES");
    else
        document.write("NO");
    
</script>

Output

YES

Performance Analysis:

Time Complexity: O(n).

Space Complexity: O(1).

Check if Queue Elements are pairwise consecutive | Set-2

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Check if X can give change to every person in the Queue

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