{"id":"ood-hash-table","title":"Design a hash map","sections":[{"id":"constraints-and-assumptions","title":"Constraints and assumptions","html":"Constraints and assumptions
\n\n- For simplicity, are the keys integers only?\n\n
\n- For collision resolution, can we use chaining?\n\n
\n- Do we have to worry about load factors?\n\n
\n- Can we assume inputs are valid or do we have to validate them?\n\n
\n- Can we assume this fits memory?\n\n
\n
","headings":[]},{"id":"solution","title":"Solution","html":"Solution
\nclass Item(object):\n\n def __init__(self, key, value):\n self.key = key\n self.value = value\n\n\nclass HashTable(object):\n\n def __init__(self, size):\n self.size = size\n self.table = [[] for _ in range(self.size)]\n\n def _hash_function(self, key):\n return key % self.size\n\n def set(self, key, value):\n hash_index = self._hash_function(key)\n for item in self.table[hash_index]:\n if item.key == key:\n item.value = value\n return\n self.table[hash_index].append(Item(key, value))\n\n def get(self, key):\n hash_index = self._hash_function(key)\n for item in self.table[hash_index]:\n if item.key == key:\n return item.value\n raise KeyError('Key not found')\n\n def remove(self, key):\n hash_index = self._hash_function(key)\n for index, item in enumerate(self.table[hash_index]):\n if item.key == key:\n del self.table[hash_index][index]\n return\n raise KeyError('Key not found')
","headings":[]}],"sourceFiles":[{"name":"hash_map.py","url":"https://github.com/donnemartin/system-design-primer/blob/master/solutions/object_oriented_design/hash_table/hash_map.py","html":"class Item(object):\n\n def __init__(self, key, value):\n self.key = key\n self.value = value\n\n\nclass HashTable(object):\n\n def __init__(self, size):\n self.size = size\n self.table = [[] for _ in range(self.size)]\n\n def _hash_function(self, key):\n return key % self.size\n\n def set(self, key, value):\n hash_index = self._hash_function(key)\n for item in self.table[hash_index]:\n if item.key == key:\n item.value = value\n return\n self.table[hash_index].append(Item(key, value))\n\n def get(self, key):\n hash_index = self._hash_function(key)\n for item in self.table[hash_index]:\n if item.key == key:\n return item.value\n raise KeyError('Key not found')\n\n def remove(self, key):\n hash_index = self._hash_function(key)\n for index, item in enumerate(self.table[hash_index]):\n if item.key == key:\n del self.table[hash_index][index]\n return\n raise KeyError('Key not found')
"}]}