reorganise directories

upd chapter_01/binary.py

chapter_04/README.md

@@ -0,0 +1,9 @@
+# Quicksort
+
+Similar to the previous recursive function, quicksort uses divide and conquer.
+
+The base case occurs for an array size 0 or 1 (doesn't need to be sorted).
+
+The recursive case works by partitioning the array around a chosen pivot repeatedly until the base case is met and then combining all sorted sub-arrays.
+
+Note. Quicksort should be implemented using a random pivot to ensure average runtimes.

chapter_04/ex4.1.py

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+class Number:
+    def __init__(self, value):
+        self.value = value
+
+
+def summation(nums):
+    if len(nums) == 1:
+        return nums[0].value
+    return nums[0].value + summation(nums[1:])
+
+
+nums = [Number(i) for i in range(0, 100, 3)]
+print(summation(nums))

chapter_04/ex4.3.py

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+import logging
+import random
+
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
+
+def maximum(nums, size):
+    if size == 1:
+        return nums[0]
+    return max(nums[size - 1], maximum(nums, size - 1))
+
+
+randomlist = random.sample(range(10, 300), 5)
+logger.debug(randomlist)
+print(maximum(randomlist, len(randomlist)))

chapter_04/ex4.4.py

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+import logging
+import random
+
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
+
+def binary_search(arr, low, high, x):
+    # x not found, low has overlapped high so we return None
+    if high < low:
+        return
+
+    mid = (high + low) // 2
+
+    # x found at middle of split, return its index
+    if arr[mid] == x:
+        return mid
+
+    # x in left side of split
+    elif arr[mid] > x:
+        return binary_search(arr, low, mid - 1, x)
+
+    # x in right side of split
+    else:
+        return binary_search(arr, mid + 1, high, x)
+
+
+LOWER = 1000
+UPPER = 1000000
+SAMPLE_SIZE = 1000
+
+numbers = random.sample(range(LOWER, UPPER), SAMPLE_SIZE)
+numbers.sort()
+
+seen = set()
+count = 0
+result = None
+while result is None:
+    guess = random.randrange(LOWER, UPPER)
+    if guess not in seen:
+        count += 1
+        seen.add(guess)
+        result = binary_search(numbers, 0, len(numbers) - 1, guess)
+
+print(f"Found {guess} at index {result} after {count} attempts.")

chapter_04/quicksort.py

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+import logging
+import random
+
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
+
+def quicksort(arr):
+    # base case. arr of length 0 or 1 don't need sorting, so return them as is
+    if len(arr) < 2:
+        return arr
+
+    pivot = arr[0]
+
+    # split arr into 3 parts, [less] | [pivot] | [greater]
+    less = [i for i in arr[1:] if i <= pivot]
+    greater = [i for i in arr[1:] if i > pivot]
+
+    return quicksort(less) + [pivot] + quicksort(greater)
+
+
+LOWER = 0
+UPPER = 100
+SAMPLE_SIZE = 15
+numbers = random.sample(range(LOWER, UPPER), SAMPLE_SIZE)
+logging.debug(numbers)
+print(quicksort(numbers))