Lemonade Change 任务调度器
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 $5.
Note that you don't have any change in hand at first.
Return true if and only if you can provide every customer with correct change.
一杯柠檬水5$,开始时没有任何钱，每个客户一次买一杯，但是可能会支付5,10,20的现金，如果现有的钱能够完成所有客户的找零，最后返回true，否则false
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.
思路
遇到需要找零的情况，先使用10+5，不够再使用5*3，原则是保留更多的5以便后面找零。
class Solution {
public boolean lemonadeChange(int[] bills) {
int cnt5= 0,cnt10 =0;
for (int bill : bills) {
switch (bill){
case 5:
cnt5+=1;
break;
case 10:
if (cnt5==0){
return false;
}
cnt5-=1;
cnt10+=1;
break;
case 20:
if(cnt5>=1&&cnt10>=1){
cnt5-=1;
cnt10-=1;
}
else if (cnt5>=3){
cnt5 = cnt5-3;
}
else {
return false;
}
break;
}
}
return true;
}
}
tag
贪心