hash table

Author: hashfx

DSA-Python/DataStructures/hashtable.py

@@ -0,0 +1,57 @@
+"""
+LookUp by key -----> O(1)
+Insertion/Deletion -----> O(1)
+
+Classes to implement HashTable in different languages:
+Python :: dictionary
+Java :: HashMap
+Java :: Linked HashMap
+C++ :: std::map
+"""
+
+class HashTable():
+    """
+    In class hashTable, an array of size '100' is created which is initialised using list_comprehension; val in each
+    element is None
+    """
+    def __init__(self):
+        self.MAX = 100  # size of array = 100
+        self.arr = [None for i in range(self.MAX)]  # list-comprehension
+
+
+    def get_hash(self, key):
+        h = 0
+        for char in key:
+            h += ord(char) # returns ASCII val of char
+        return h%self.MAX  # hash: Sum(ASCII_Values(key)) % size(array)
+
+    def add(self, key, val):
+        h = self.get_hash(key) # retrieving hash function
+        self.arr[h] = val
+
+    def get(self, key):
+        h = self.get_hash(key)
+        return self.arr[h]
+
+    def delete(self, key):
+        h = self.get_hash(key)
+        self.arr[h] = None
+
+
+
+
+t = HashTable()  # object of class HashTable
+q = t.add('Google', 120)
+r = t.get('Google')
+# s = t.arr  # to get full array
+# m = t.delete('Google')  # delete element by key
+# n = t.arr  # to get full array after deleting
+print(r)
+
+# todo Collision Handling
+# Collision Handling: When one or more elements are assigned the same hash
+
+s = t.add('Google', 121)
+z = t.get('Google')
+print(z)
+