算法分析與設計第九周作業
題目
t 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.
題目傳送門
解答
很簡單的貪心算法，只用先給大的，再給小的就可以了。
class Solution {
public:
bool lemonadeChange(vector<int>& bills) {
unsigned five_cash_cnt = 0;
unsigned ten_cash_cnt = 0;
for (const int bill : bills)
{
switch (bill)
{
case 5:
five_cash_cnt++;
break;
case 10:
if (!five_cash_cnt)
{
return false;
}
five_cash_cnt--;
ten_cash_cnt++;
break;
case 20:
if (ten_cash_cnt && five_cash_cnt)
{
ten_cash_cnt--;
five_cash_cnt--;
}
else if (five_cash_cnt > 2)
{
five_cash_cnt -= 3;
}
else
{
return false;
}
break;
}
}
return true;
}
};