Hash djb2 (TheAlgorithms#2098)

* implement hash * fix flake8 error * Update hashes/djb2.py * Update hashes/djb2.py * Long lines * def djb2(s: str) -> int: Co-authored-by: Christian Clauss <[email protected]>
priteshk · Jun 16, 2020 · 62f7561 · 62f7561
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diff --git a/hashes/djb2.py b/hashes/djb2.py
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+"""
+This algorithm (k=33) was first reported by Dan Bernstein many years ago in comp.lang.c
+Another version of this algorithm (now favored by Bernstein) uses xor:
+    hash(i) = hash(i - 1) * 33 ^ str[i];
+
+    First Magic constant 33:
+    It has never been adequately explained.
+    It's magic because it works better than many other constants, prime or not.
+
+    Second Magic Constant 5381:
+
+    1. odd number
+    2. prime number
+    3. deficient number
+    4. 001/010/100/000/101 b
+
+    source: http://www.cse.yorku.ca/~oz/hash.html
+"""
+
+
+def djb2(s: str) -> int:
+    """
+    Implementation of djb2 hash algorithm that
+    is popular because of it's magic constants.
+
+    >>> djb2('Algorithms')
+    3782405311
+
+    >>> djb2('scramble bits')
+    1609059040
+    """
+    hash = 5381
+    for x in s:
+        hash = ((hash << 5) + hash) + ord(x)
+    return hash & 0xFFFFFFFF