Working on linear time sorting.

interview/generate_numbers.py

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+"""
+Generate 1,000,000 unique numbers from 0 to 9,999,999
+"""
+
+import random
+
+
+def main():
+    numbers = random.sample(range(9999999), 100)
+    open("numbers.txt", "w")\
+        .write("\n".join(str(n) for n in numbers))
+
+
+if __name__ == "__main__":
+    main()

interview/sorting_linear.py

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+"""
+Implement an algorithm to sort 1,000,000 32-bit integers, using only 350K of memory.
+The numbers could be any number from 0 to 9,999,999
+The numbers are in a file, one line per number. There are no duplicates.
+Output the numbers, one to a line, to a file.
+The algorithm must be linear-time.
+"""
+
+
+class Bitsort(object):
+
+    def __init__(self, max_number):
+        self._int_bits = 32
+        self._buckets = (max_number // self._int_bits) + 1
+        self._bit_array = [0] * self._buckets
+
+    def save_number(self, number):
+        bucket = number // self._int_bits
+        bit_number = number % self._int_bits
+        self._bit_array[bucket] |= 1 << bit_number
+
+    def get_sorted_numbers(self):
+        for index, bits in enumerate(self._bit_array):
+            base = index * self._int_bits
+
+            if not bits:  # skips empty buckets
+                continue
+
+            for j in range(self._int_bits):
+                if bits & (1 << j):
+                    yield base + j
+
+
+def main():
+    bitsorter = Bitsort(9999999)
+
+    with open("numbers.txt", "r") as in_file:
+        for line in in_file:
+            bitsorter.save_number(int(line.rstrip()))
+
+    out_file = open("out.txt", "w")
+    for number in bitsorter.get_sorted_numbers():
+        out_file.write(str(number) + "\n")
+
+
+if __name__ == "__main__":
+    main()