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Author: wuduhren

problems/find-original-array-from-doubled-array,py

@@ -0,0 +1,26 @@
+"""
+Time: O(NLogN)
+Space: O(N)
+"""
+class Solution(object):
+    def findOriginalArray(self, changed):
+        if len(changed)%2!=0: return []
+        
+        ans = []
+        counter = collections.Counter() #store the count of the doubled number
+        count = 0 #sum of count in counter
+        
+        changed.sort() #need to be sorted, otherwise we cannot identify which number is orginal or it is doubled.
+        
+        for num in changed:
+            if counter[num]>0:
+                #num is a doubled num
+                counter[num] -= 1
+                count -= 1
+                ans.append(num/2)
+            else:
+                #num is an original num
+                counter[num*2] += 1
+                count += 1
+        
+        return ans if count==0 else []

problems/logger-rate-limiter.py

@@ -0,0 +1,10 @@
+class Logger(object):
+    def __init__(self):
+        self.log = collections.Counter() #store the latest timestamp
+
+    def shouldPrintMessage(self, timestamp, message):
+        if message not in self.log or self.log[message]+10<=timestamp:
+            self.log[message] = timestamp
+            return True
+        else:
+            return False