Garrett Heiner

recursive-search.py

@@ -0,0 +1,36 @@
+''''
+MATHEMATICS•LINGUISTICS
+relating to or involving the repeated application of a rule, definition, or procedure to successive results.
+"this restriction ensures that the grammar is recursive"
+COMPUTING
+relating to or involving a program or routine of which a part requires the application of the whole, so that its explicit interpretation requires in general many successive executions.
+"a recursive subroutine"
+'''
+# Example 4:
+# Input: nums = [-1, 0, 3, 5, 9, 12], target = -1
+# Output: 0
+# Explanation: -1 exists in the list and its index is 0
+
+def recursive_binary_search(arr, target):
+    if len(arr) == 0:
+        return -1
+
+    # find the middle index
+    mid_idx = int(len(arr) / 2)
+    # check if mid index equals target
+    middle = arr[mid_idx]
+
+    if middle == target:
+        return mid_idx
+    elif middle > target:
+        # check idx 0 - mid_idx
+        return recursive_binary_search(arr[:mid_idx], target)
+    else:
+        # check mid_idx + 1 - last idx
+        result = recursive_binary_search(arr[mid_idx + 1:], target)
+        if result == -1:
+            return -1
+        else:
+            return result + mid_idx + 1
+
+print(recursive_binary_search([-1, 0, 3, 5, 9, 12], 5))

search.py

@@ -19,3 +19,82 @@
 Output: 0
 Explanation: -1 exists in the list and its index is 0
 """
+
+# def binary_search(arr, target):
+    # # keep track of minimum of the range
+    # min_idx = 0
+    # # keep track of the max of the range
+    # max_idx = len(arr) - 1
+
+    # # loop this until value is found, or where index would be
+    # while min_idx < max_idx:
+    #     # keep track of the middle of the range
+    #     mid_idx = int((min_idx + max_idx) / 2)
+    #     middle = arr[mid_idx]
+    #     # check if middle of the range equals target
+    #     if middle == target:
+    #         return mid_idx
+    #     # if mid < target, narrow in on right side
+    #     elif middle < target:
+    #         min_idx = mid_idx + 1
+    #         # print(arr[mid_idx])
+    #     # if mid > target, narrow in on left half
+    #     else:
+    #         max_idx = mid_idx - 1
+    #         # print(arr[mid_idx])
+    # # returns -1 if target not found in array
+    # return -1
+
+def binary_search(nums, target):
+    # keep track of the window -- start by assuming the entire list is the window
+    # vars for low idx of window, high idx of window, mid idx of window
+    low = 0
+    high = len(nums)
+    mid = high // 2
+
+    if target == nums[0]:
+        return 0
+
+    # continue to iterate until the target is found or is not here
+    while True:
+        # check the value at mid idx against target, stop if equal
+        if nums[mid] == target:
+            return mid
+        # if the value at the mid idx is less than target, slide window left
+        elif nums[mid] > target:
+            high = mid
+            difference = high - low
+            mid = low + (difference // 2)
+        # otherwise slid to right
+        else:
+            low = mid
+            difference = high - low
+            mid = low + (difference // 2)
+    print(f"low: {low}, mid: {mid}, high: {high}")
+    # stop iteration when the mid value is equal to low or high becasue we did not find it
+    if mid <= low or mid >= high:
+        return -1
+
+print(binary_search([-1, 0, 3, 5, 9, 12], 2))
+
+"""
+Example 1:
+Input: nums = [-1, 0, 3, 5, 9, 12], target = 9
+Output: 4
+Explanation: 9 exists in nums and its index is 4
+
+Example 2:
+Input: nums = [-1, 0, 3, 5, 9, 12], target = 2
+Output: -1
+Explanation: 2 does not exist in nums so return -1
+
+Example 3:
+Input: nums = [-1, 0, 3, 5, 9, 12], target = 12
+Output: 5
+Explanation: 12 exists in the list and its index is 5
+
+Example 4:
+Input: nums = [-1, 0, 3, 5, 9, 12], target = -1
+Output: 0
+Explanation: -1 exists in the list and its index is 0
+"""