Fixes: fix the code to return tuple so we can add doctests in it and …

dynamic_programming/subset_generation.py

@@ -1,44 +1,48 @@
-# Print all subset combinations of n element in given set of r element.
+from typing import List, Tuple, Union
 
 
-def combination_util(arr, n, r, index, data, i):
+def combination_util(
+    arr: List[int], n: int, r: int, index: int, data: List[int], i: int
+) -> Union[Tuple[int, ...], None]:
     """
-    Current combination is ready to be printed, print it
-    arr[]  ---> Input Array
-    data[] ---> Temporary array to store current combination
-    start & end ---> Staring and Ending indexes in arr[]
-    index  ---> Current index in data[]
-    r ---> Size of a combination to be printed
+    Generate all combinations of 'r' elements from a given set of 'n' elements.
+
+    :param arr: List of input elements
+    :param n: Number of elements in the input list
+    :param r: Size of the combination to be generated
+    :param index: Current index in the 'data' list
+    :param data: Temporary list to store the current combination
+    :param i: Current index in the 'arr' list
+    :return: A tuple representing a combination of 'r' elements, or None if no more combinations are possible.
     """
     if index == r:
-        for j in range(r):
-            print(data[j], end=" ")
-        print(" ")
-        return
-    #  When no more elements are there to put in data[]
+        return tuple(data)
     if i >= n:
-        return
-    # current is included, put next at next location
+        return None
     data[index] = arr[i]
-    combination_util(arr, n, r, index + 1, data, i + 1)
-    # current is excluded, replace it with
-    # next (Note that i+1 is passed, but
-    # index is not changed)
-    combination_util(arr, n, r, index, data, i + 1)
-    # The main function that prints all combinations
-    # of size r in arr[] of size n. This function
-    # mainly uses combinationUtil()
-
-
-def print_combination(arr, n, r):
-    # A temporary array to store all combination one by one
+    res1 = combination_util(arr, n, r, index + 1, data, i + 1)
+    res2 = combination_util(arr, n, r, index, data, i + 1)
+    if res1 is None:
+        return res2
+    elif res2 is None:
+        return res1
+    else:
+        return res1, res2
+
+
+def get_combinations(arr: List[int], n: int, r: int) -> List[Tuple[int, ...]]:
+    """
+    Generate all combinations of 'r' elements from the given list of elements.
+
+    :param arr: List of input elements
+    :param n: Number of elements in the input list
+    :param r: Size of the combination to be generated
+    :return: A list of tuples representing combinations of 'r' elements.
+    """
     data = [0] * r
-    # Print all combination using temporary array 'data[]'
-    combination_util(arr, n, r, 0, data, 0)
+    return combination_util(arr, n, r, 0, data, 0)
 
 
 if __name__ == "__main__":
-    # Driver code to check the function above
     arr = [10, 20, 30, 40, 50]
-    print_combination(arr, len(arr), 3)
-    # This code is contributed by Ambuj sahu
+    print(get_combinations(arr, len(arr), 3))