Create 0860_Lemonade_Change.cpp

Author: xinye83

Cpp/0860_Lemonade_Change.cpp

@@ -0,0 +1,83 @@
+/*
+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.
+*/
+
+class Solution {
+public:
+    bool lemonadeChange(vector<int>& bills) {
+        vector<int> change(2,0);
+        for (int i = 0; i < bills.size(); ++i) {
+            if (bills[i] == 5) {
+                change[0]++;
+            }
+            else if (bills[i] == 10) {
+                if (change[0] == 0) {
+                    return false;
+                }
+                
+                change[0]--;
+                change[1]++;
+            }
+            else {
+                if (change[1] > 0 && change[0] > 0) {
+                    change[0]--;
+                    change[1]--;
+                }
+                else if (change[0] > 3) {
+                    change[0] -= 3;
+                }
+                else {
+                    return false;
+                }
+            }
+        }
+        
+        return true;
+    }
+};