Description：

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: trueExplanation: 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: falseExplanation: 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.

1. 顾客支付5\$，无需找零
2. 顾客支付10\$，找给顾客5\$
3. 顾客支付20\$，找给顾客10\$ + 5\$，或者3张5\$

##### Java
`class Solution {    public boolean lemonadeChange(int[] bills) {        int fiveCnt = bills[0] == 5 ? 1 : 0;        int tenCnt = bills[0] == 10 ? 1 : 0;        for (int i = 1; i < bills.length; i++) {            if (bills[i] == 5) {                fiveCnt++;            } else if (bills[i] == 10 && fiveCnt > 0) {                fiveCnt--;                tenCnt++;            } else if (fiveCnt > 0 && tenCnt > 0){                fiveCnt--;                tenCnt--;            } else if (fiveCnt > 2) {                fiveCnt -= 3;            } else {                return false;            }        }        return true;    }}`