⛓ pull

src/searching/searching.py

@@ -1,7 +1,33 @@
 # TO-DO: Implement a recursive implementation of binary search
 def binary_search(arr, target, start, end):
+
     # Your code here
 
+# we need to call this function in itself
+# each recursive call should bring us closer to reaching
+# the base case(s)
+# base case(s): when does the recursion stop?
+# it stops when we find the target
+# or start and go past each other (i.e. we didn't find the target)
+
+    if start > end:
+        # if target isn't in the array
+        return -1
+    else: 
+        mid = (start + end) // 2
+        if arr[mid] == target:
+            # this is our second base case
+            return mid
+        # otherwise we need to move towards one of our base cases
+        # arr doesn't change, just because we'll end updating start and end target 
+        # doesn't change between recursive calls
+        # and changes if we're tossing out the right side of the array
+        elif arr[mid] > target:
+            binary_search(arr, target, start, mid - 1) 
+
+        else:
+            return binary_search(arr, target, mid + 1, end)    
+
 
 # STRETCH: implement an order-agnostic binary search
 # This version of binary search should correctly find 
@@ -10,5 +36,4 @@ def binary_search(arr, target, start, end):
 # You can implement this function either recursively 
 # or iteratively
 def agnostic_binary_search(arr, target):
-    # Your code here
-
+    # Your code here