Create design-hashmap.py

Author: kamyu104

Python/design-hashmap.py

@@ -0,0 +1,125 @@
+# Time:  O(1)
+# Space: O(n)
+
+# Design a HashMap without using any built-in hash table libraries.
+#
+# To be specific, your design should include these two functions:
+#
+# put(key, value) : Insert a (key, value) pair into the HashMap.
+#                   If the value already exists in the HashMap, update the value.
+# get(key): Returns the value to which the specified key is mapped,
+#           or -1 if this map contains no mapping for the key.
+# remove(key) : Remove the mapping for the value key if this map contains the mapping for the key.
+#
+# Example:
+#
+# MyHashMap hashMap = new MyHashMap();
+# hashMap.put(1, 1);          
+# hashMap.put(2, 2);         
+# hashMap.get(1);            // returns 1
+# hashMap.get(3);            // returns -1 (not found)
+# hashMap.put(2, 1);          // update the existing value
+# hashMap.get(2);            // returns 1 
+# hashMap.remove(2);          // remove the mapping for 2
+# hashMap.get(2);            // returns -1 (not found) 
+#
+# Note:
+# - All values will be in the range of [1, 1000000].
+# - The number of operations will be in the range of [1, 10000].
+# - Please do not use the built-in HashMap library.
+
+
+class ListNode(object):
+    def __init__(self, key, val):
+        self.val = val
+        self.key = key
+        self.next = None
+        self.prev = None
+
+
+class LinkedList(object):
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+    def insert(self, node):
+        node.next, node.prev = None, None  # avoid dirty node
+        if self.head is None:
+            self.head = node
+        else:
+            self.tail.next = node
+            node.prev = self.tail
+        self.tail = node
+
+    def delete(self, node):
+        if node.prev:
+            node.prev.next = node.next
+        else:
+            self.head = node.next
+        if node.next:
+            node.next.prev = node.prev
+        else:
+            self.tail = node.prev
+        node.next, node.prev = None, None  # make node clean
+
+    def find(self, key):
+        curr = self.head
+        while curr:
+            if curr.key == key:
+                break
+            curr = curr.next
+        return curr
+
+
+class MyHashMap(object):
+
+    def __init__(self):
+        """
+        Initialize your data structure here.
+        """
+        self.__data = [LinkedList() for _ in xrange(10000)]
+
+    def put(self, key, value):
+        """
+        value will always be positive.
+        :type key: int
+        :type value: int
+        :rtype: void
+        """
+        l = self.__data[key % len(self.__data)]
+        node = l.find(key)
+        if node:
+            node.val = value
+        else:
+            l.insert(ListNode(key, value))
+
+    def get(self, key):
+        """
+        Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key
+        :type key: int
+        :rtype: int
+        """
+        l = self.__data[key % len(self.__data)]
+        node = l.find(key)
+        if node:
+            return node.val
+        else:
+            return -1
+
+    def remove(self, key):
+        """
+        Removes the mapping of the specified value key if this map contains a mapping for the key
+        :type key: int
+        :rtype: void
+        """
+        l = self.__data[key % len(self.__data)]
+        node = l.find(key)
+        if node:
+            l.delete(node)
+
+
+# Your MyHashMap object will be instantiated and called as such:
+# obj = MyHashMap()
+# obj.put(key,value)
+# param_2 = obj.get(key)
+# obj.remove(key)