add recursive soln.

03_recursion/python/04_count.py

@@ -0,0 +1,4 @@
+def count(arr):
+    if not arr:
+        return 0
+    return 1 + count(arr[1:])

03_recursion/python/05_binary_search_recursive.py

@@ -0,0 +1,15 @@
+def binary_search(arr, target):
+    if not arr:
+        return -1        
+    if len(arr) == 1 and arr[0] == target:
+        return arr[0]
+    if len(arr) == 1 and arr[0] != target:
+        return -1
+    low = 0         
+    high = len(arr) - 1    
+    mid = (low + high) // 2
+
+    if arr[mid] > target:
+        return binary_search(arr[:mid], target)
+    else:
+        return binary_search(arr[mid+1:], target)

03_recursion/python/06_find_max.py

@@ -0,0 +1,5 @@
+def find_max(arr):
+    if len(arr) == 2:
+        return arr[0] if arr[0] > arr[1] else arr[1]
+    sub_max = find_max(arr[1:])
+    return arr[0] if arr[0] > sub_max else sub_max

03_recursion/python/07_sum_array.py

@@ -0,0 +1,4 @@
+def sum_array(arr):
+    if not arr:
+        return 0
+    return arr[0] + sum_array(arr[1:])