Searching

Author: ivanmmarkovic

searching/binary-search-iterative.py

@@ -0,0 +1,20 @@
+
+def binary_search(nums: list, target: int) -> bool:
+    start: int = 0
+    end: int = len(nums) - 1
+    found: bool = False
+    while start <= end and not found:
+        midpoint: int = start + (end - start) // 2
+        if nums[midpoint] == target:
+            found = True
+        else:
+            if nums[midpoint] > target:
+                end = midpoint - 1
+            else:
+                start = midpoint + 1
+    return found
+
+
+testlist = [0, 1, 2, 8, 13, 17, 19, 32, 42]
+print(binary_search(testlist, 3))
+print(binary_search(testlist, 13))

searching/binary-search-recursive-pointers.py

@@ -0,0 +1,22 @@
+
+def binary_search(nums: list, target: int) -> bool:
+
+    def binary_search_helper(numbers: list, element, start: int, end: int) -> bool:
+        if start > end:
+            return False
+        else:
+            midpoint: int = start + (end - start) // 2
+            if nums[midpoint] == element:
+                return True
+            else:
+                if nums[midpoint] > element:
+                    return binary_search_helper(numbers, element, start, midpoint - 1)
+                else:
+                    return binary_search_helper(numbers, element, midpoint + 1, end)
+
+    return binary_search_helper(nums, target, 0, len(nums) - 1)
+
+
+testlist = [0, 1, 2, 8, 13, 17, 19, 32, 42]
+print(binary_search(testlist, 3))
+print(binary_search(testlist, 13))

searching/binary-search-recursive.py

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+# slicing a list is O(k)
+# better is recursive solution with pointers
+def binary_search(nums: list, target: int) -> bool:
+    if len(nums) == 0:
+        return False
+    else:
+        midpoint: int = len(nums) // 2
+        if nums[midpoint] == target:
+            return True
+        else:
+            if nums[midpoint] > target:
+                return binary_search(nums[0: midpoint], target)
+            else:
+                return binary_search(nums[midpoint + 1:], target)
+
+
+testlist = [0, 1, 2, 8, 13, 17, 19, 32, 42]
+print(binary_search(testlist, 3))
+print(binary_search(testlist, 13))

searching/sequential-search-ordered-list.py

@@ -0,0 +1,19 @@
+
+def sequential_search(nums: list, target: int) -> bool:
+    found: bool = False
+    stopped: bool = False
+    i: int = 0
+    while i < len(nums) and not found and not stopped:
+        if nums[i] == target:
+            found = True
+        else:
+            if nums[i] > target:
+                stopped = True
+            else:
+                i += 1
+    return found
+
+
+testlist = [0, 1, 2, 8, 13, 17, 19, 32, 42]
+print(sequential_search(testlist, 3))
+print(sequential_search(testlist, 13))

searching/sequential-search-unordered-list.py

@@ -0,0 +1,15 @@
+
+def sequential_search(nums: list, target: int) -> bool:
+    i: int = 0
+    found: bool = False
+    while i < len(nums) and not found:
+        if nums[i] == target:
+            found = True
+        else:
+            i += 1
+    return found
+
+
+testlist = [1, 2, 32, 8, 17, 19, 42, 13, 0]
+print(sequential_search(testlist, 3))
+print(sequential_search(testlist, 13))