860. Lemonade Change --E

Q:

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.

Return true if and only if you can provide every customer with correct change.

 

Example 1:

Input: [5,5,5,10,20]
Output: true
Explanation: 
From the first 3 customers, we collect three $5 bills in order.
From the fourth customer, we collect a $10 bill and give back a $5.
From the fifth customer, we give a $10 bill and a $5 bill.
Since all customers got correct change, we output true.

Example 2:

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

Example 3:

Input: [10,10]
Output: false

Example 4:

Input: [5,5,10,10,20]
Output: false
Explanation: 
From the first two customers in order, we collect two $5 bills.
For the next two customers in order, we collect a $10 bill and give back a $5 bill.
For the last customer, we can't give change of $15 back because we only have two $10 bills.
Since not every customer received correct change, the answer is false.

 

Note:

• 0 <= bills.length <= 10000
• bills[i] will be either 5, 10, or 20.

A:

class Solution {
public:
    bool lemonadeChange(vector<int>& bills) {
        int c5 = 0, c10=0;
        for(auto k : bills){
            if(k == 5)
                c5++;
            if(k == 10)
                c10++;
            
            int change = k - 5;
            while(change >0){
                if(change >=10 && c10 >0)
                {
                    --c10;
                    change -= 10;
                }else if(c5>0){
                    --c5;
                    change -= 5;
                }else{
                    return false;
                }
            }
        }
        return true;
        
    }
};

一开始忘了   c5++ 和c10 ++