Dp subset tests Closes #9943

.gitignore

@@ -86,6 +86,7 @@ celerybeat-schedule
 .venv
 env/
 venv/
+myenv/
 ENV/
 env.bak/
 venv.bak/

dynamic_programming/subset_generation.py

@@ -1,44 +1,87 @@
 # Print all subset combinations of n element in given set of r element.
 
 
-def combination_util(arr, n, r, index, data, i):
+def combination_util(arr, n, r, index, data, i, results):
     """
     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
+
+    >>> combination_util([1, 2, 3], 3, 2, 0, [0, 0], 0, [])
+    [[1, 2], [1, 3], [2, 3]]
+    >>> combination_util([-1,-2,-3], 3, 2, 0, [0, 0], 0, [])
+    [[-1, -2], [-1, -3], [-2, -3]]
+
+    >>> combination_util([], 0, 2, 0, [0, 0], 0, [])
+
+    >>> combination_util([1], 1, 2, 0, [0, 0], 0, [])
+    []
+
+
     """
+
     if index == r:
-        for j in range(r):
-            print(data[j], end=" ")
-        print(" ")
-        return
+        results.append(data[:r])
+
     #  When no more elements are there to put in data[]
-    if i >= n:
+    elif i >= n:
         return
     # current is included, put next at next location
-    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()
+    else:
+        data[index] = arr[i]
+        combination_util(arr, n, r, index + 1, data, i + 1, results)
+        # 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, results)
+        # The main function that prints all combinations
+        # of size r in arr[] of size n. This function
+        # mainly uses combinationUtil()
+
+    return results
 
 
 def print_combination(arr, n, r):
+    """
+    >>> print_combination([1, 2, 3], 3, 2)
+    [[1, 2], [1, 3], [2, 3]]
+    >>> print_combination([-1,-2,-3], 3, 2)
+    [[-1, -2], [-1, -3], [-2, -3]]
+
+    >>> print_combination([], 3, 2)
+
+    >>> print_combination([1], 3, 2)
+
+    >>> print_combination([1, 2, 2], 3, 2)
+    [[1, 2], [1, 2], [2, 2]]
+
+    >>> print_combination(['a', 'b', 'c'], 3, 2)
+    [['a', 'b'], ['a', 'c'], ['b', 'c']]
+
+    >>> print_combination([1, 'a', 2], 3, 2)
+    [[1, 'a'], [1, 2], ['a', 2]]
+
+    """
     # A temporary array to store all combination one by one
+    # returns nothing if n < r
+    if len(arr) < r:
+        return
     data = [0] * r
     # Print all combination using temporary array 'data[]'
-    combination_util(arr, n, r, 0, data, 0)
+    results = []
+    (combination_util(arr, n, r, 0, data, 0, results))
+    return results
 
 
 if __name__ == "__main__":
     # Driver code to check the function above
+    # arr = [10,20,30,40,50]
     arr = [10, 20, 30, 40, 50]
-    print_combination(arr, len(arr), 3)
+    results = print_combination(arr, len(arr), 3)
+
+    for combo in results:
+        print(" ".join(map(str, combo)))
     # This code is contributed by Ambuj sahu