From 0a1c70bab24e7451b2c9af4bc5e7caf17157a5b5 Mon Sep 17 00:00:00 2001
From: diego95root <minidiego@ono.com>
Date: Fri, 11 Oct 2019 12:46:40 +0100
Subject: [PATCH] Added radix sort sorting algorithm

---
 algorithms/sorting/radix_sort.py | 45 ++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 algorithms/sorting/radix_sort.py

diff --git a/algorithms/sorting/radix_sort.py b/algorithms/sorting/radix_sort.py
new file mode 100644
index 00000000..33303411
--- /dev/null
+++ b/algorithms/sorting/radix_sort.py
@@ -0,0 +1,45 @@
+"""
+Radix sort does sorting by going digit to digit from the least significant to the most
+significant one. Its running time is dependant on the base and if it's a big base it can
+run in O(n). Otherwise we get O((n+b) * logb(k)), see https://www.geeksforgeeks.org/radix-sort/
+for an explanation.
+"""
+
+from math import log10
+from random import randint
+
+def get_digit(number, base, pos):
+  return (number // base ** pos) % base
+
+def prefix_sum(array):
+  for i in range(1, len(array)):
+    array[i] = array[i] + array[i-1]
+  return array
+
+def radixsort(l, base=10):
+  passes = int(log10(max(l))+1)
+  output = [0] * len(l)
+
+  for pos in range(passes):
+    count = [0] * base
+
+    for i in l:
+      digit = get_digit(i, base, pos)
+      count[digit] +=1
+
+    count = prefix_sum(count)
+
+    for i in reversed(l):
+      digit = get_digit(i, base, pos)
+      count[digit] -= 1
+      new_pos = count[digit]
+      output[new_pos] = i
+
+    l = list(output)
+  return output
+
+bef = [12,54,23,78,120,3423,342]
+new = radixsort(bef)
+
+print bef
+print new