Lemonade Change

At a lemonade stand, each lemonade costs $5. 
Customers are standing in a queue to buy from you, and order one at a time (in the order specified by bills).
Each customer will only buy one lemonade and pay with either a $5, $10, or $20 bill.  You must provide the correct change to each customer so that the net transaction is that the customer pays $5.
Note that you don't have any change in hand at first

 Example 1:

Input: [5,5,5,10,20]
Output: true

Approach

Java

public class LemonadeChange {
    public static void main(String[] args) {
        int arr[] = { 5, 5, 5, 10, 20 };
        System.out.println(lemonadeChange(arr));
    }

    // function to check for
    // lemando change
    static boolean lemonadeChange(int[] bills) {
        int cnt5 = 0, cnt10 = 0;
        int flag = 0;
        for (int i = 0; i < bills.length; i++) {
            if (bills[i] == 5)
                cnt5++;
            else if (bills[i] == 10) {
                if (cnt5 == 0) {
                    flag = 1;
                    break;
                } else {
                    cnt5--;
                    cnt10++;
                }
            } else if (bills[i] == 20) {
                if (cnt5 == 0) {
                    flag = 1;
                    break;
                } else if (cnt10 == 0 && cnt5 < 3) {
                    flag = 1;
                    break;
                } else if (cnt10 == 0) {

                    cnt5 -= 3;
                } else if (cnt10 > 0) {
                    cnt10--;
                    cnt5--;
                }
            }
        }
        if (flag == 0)
            return true;
        return false;
    }

}

C++

#include <bits/stdc++.h>
using namespace std;

//function to check for
//lemando change 
bool lemonadeChange(vector<int>& bills) 
 {
      int cnt5=0,cnt10=0;
        int flag=0;
      for(int i=0;i<bills.size();i++)
       {
          if(bills[i]==5)
                cnt5++;
          else if(bills[i]==10)
          {
              if(cnt5==0)
              {
                  flag=1;
                  break;
              }
              else
              {
                  cnt5--;
                  cnt10++;
              }
          }
          else if(bills[i]==20)
          {
              if(cnt5==0)
              {
                  flag=1;
                  break;
              }
             else if(cnt10==0 &&cnt5<3)
             {
                 flag=1;
                 break;
             }
            else if(cnt10==0)
            {
                
                cnt5-=3;
            }
             else if(cnt10>0)
             {
                 cnt10--;
                 cnt5--;
             }
          }
       }
    if(flag==0)
          return true;
        return false;
}

int main()
{
   vector<int> arr={5,5,5,10,20};
   if(lemonadeChange(arr))
     cout<<"true";
   else
    cout<<"false";
   
   return 0;
}