#15 deterministic_search, scramble_search

src/book/chapter5/problem2.py

@@ -0,0 +1,43 @@
+from typing import Optional
+
+from book.chapter5.section3 import randomly_permute
+from book.data_structures import Array
+from util import range_of
+
+
+def deterministic_search(A: Array, n: int, x: int) -> Optional[int]:
+    """Searches for a value in an array, examining its elements sequentially.
+
+    Implements:
+        Deterministic-Search
+
+    Args:
+        A: an Array to search through
+        n: the number of numbers in array A
+        x: the value to search for
+
+    Returns:
+        An index i such that x equals A[i] or None if x does not appear in A.
+    """
+    for i in range_of(1, to=n):
+        if A[i] == x:
+            return i
+    return None
+
+
+def scramble_search(A: Array, n: int, x: int) -> Optional[int]:
+    """Searches for a value in an array by first permuting it, then examining its elements sequentially.
+
+    Implements:
+        Scramble-Search
+
+    Args:
+        A: an Array to search through
+        n: the number of numbers in array A
+        x: the value to search for
+
+    Returns:
+        An index i such that x equals A[i] or None if x does not appear in A.
+    """
+    randomly_permute(A, n)
+    return deterministic_search(A, n, x)

test/test_book/test_chapter5.py

@@ -8,6 +8,8 @@
 from hypothesis.strategies import lists
 
 from book.chapter5.problem1 import increment
+from book.chapter5.problem2 import deterministic_search
+from book.chapter5.problem2 import scramble_search
 from book.chapter5.section1 import hire_assistant
 from book.chapter5.section3 import permute_by_cycle
 from book.chapter5.section3 import permute_with_all
@@ -160,3 +162,31 @@ def test_online_maximum(self, data):
         if actual_maximum_position < n:
             for i in range_of(1, to=k):
                 self.assertGreater(score[actual_maximum_position], score[i])
+
+    @given(st.data())
+    def test_deterministic_search(self, data):
+        elements = data.draw(lists(integers(min_value=-10, max_value=10), min_size=1, max_size=20))
+        x = data.draw(integers(min_value=-10, max_value=10))
+        A = create_array(elements)
+        n = len(elements)
+
+        actual_index = deterministic_search(A, n, x)
+
+        if actual_index:
+            self.assertEqual(A[actual_index], x)
+        else:
+            self.assertNotIn(x, elements)
+
+    @given(st.data())
+    def test_scramble_search(self, data):
+        elements = data.draw(lists(integers(min_value=-10, max_value=10), min_size=1, max_size=20))
+        x = data.draw(integers(min_value=-10, max_value=10))
+        A = create_array(elements)
+        n = len(elements)
+
+        actual_index = scramble_search(A, n, x)
+
+        if actual_index:
+            self.assertEqual(A[actual_index], x)
+        else:
+            self.assertNotIn(x, elements)