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Lemonade Change.cpp
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Lemonade Change.cpp
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Task: 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.
Solution:
class Solution {
public:
bool lemonadeChange(vector<int>& bills) {
int i=0,flag=0,five_cnt=0,ten_cnt=0,twenty_cnt=0;
while(i<bills.size()){
if(bills[i]==5){
five_cnt+=1;
}
else if(bills[i]==10){
if(five_cnt!=0){
ten_cnt+=1;
five_cnt-=1;
}
else{
flag=1;
break;
}
}
else{
if(ten_cnt!=0&&five_cnt!=0){
twenty_cnt+=1;
ten_cnt-=1;
five_cnt-=1;
}
else if(five_cnt>2){
twenty_cnt+=1;
five_cnt-=3;
}
else{
flag=1;
break;
}
}
i++;
}
if(flag==0){
return true;
}
else{
return false;
}
}
};