Fixes #9943 (#10252)

* added doctest for all_permutations.py

* added doctest for all_subsequences.py

* added doctest for all_subsequences.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* doctest added

* updated

* Update backtracking/all_subsequences.py

---------

Co-authored-by: Harsh Buddhdev <harshbuddhdev5@.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

backtracking/all_permutations.py

@@ -23,6 +23,42 @@ def create_state_space_tree(
     Creates a state space tree to iterate through each branch using DFS.
     We know that each state has exactly len(sequence) - index children.
     It terminates when it reaches the end of the given sequence.
+
+    :param sequence: The input sequence for which permutations are generated.
+    :param current_sequence: The current permutation being built.
+    :param index: The current index in the sequence.
+    :param index_used: list to track which elements are used in permutation.
+
+    Example 1:
+    >>> sequence = [1, 2, 3]
+    >>> current_sequence = []
+    >>> index_used = [False, False, False]
+    >>> create_state_space_tree(sequence, current_sequence, 0, index_used)
+    [1, 2, 3]
+    [1, 3, 2]
+    [2, 1, 3]
+    [2, 3, 1]
+    [3, 1, 2]
+    [3, 2, 1]
+
+    Example 2:
+    >>> sequence = ["A", "B", "C"]
+    >>> current_sequence = []
+    >>> index_used = [False, False, False]
+    >>> create_state_space_tree(sequence, current_sequence, 0, index_used)
+    ['A', 'B', 'C']
+    ['A', 'C', 'B']
+    ['B', 'A', 'C']
+    ['B', 'C', 'A']
+    ['C', 'A', 'B']
+    ['C', 'B', 'A']
+
+    Example 3:
+    >>> sequence = [1]
+    >>> current_sequence = []
+    >>> index_used = [False]
+    >>> create_state_space_tree(sequence, current_sequence, 0, index_used)
+    [1]
     """
 
     if index == len(sequence):

backtracking/all_subsequences.py

@@ -22,6 +22,56 @@ def create_state_space_tree(
     Creates a state space tree to iterate through each branch using DFS.
     We know that each state has exactly two children.
     It terminates when it reaches the end of the given sequence.
+
+    :param sequence: The input sequence for which subsequences are generated.
+    :param current_subsequence: The current subsequence being built.
+    :param index: The current index in the sequence.
+
+    Example:
+    >>> sequence = [3, 2, 1]
+    >>> current_subsequence = []
+    >>> create_state_space_tree(sequence, current_subsequence, 0)
+    []
+    [1]
+    [2]
+    [2, 1]
+    [3]
+    [3, 1]
+    [3, 2]
+    [3, 2, 1]
+
+    >>> sequence = ["A", "B"]
+    >>> current_subsequence = []
+    >>> create_state_space_tree(sequence, current_subsequence, 0)
+    []
+    ['B']
+    ['A']
+    ['A', 'B']
+
+    >>> sequence = []
+    >>> current_subsequence = []
+    >>> create_state_space_tree(sequence, current_subsequence, 0)
+    []
+
+    >>> sequence = [1, 2, 3, 4]
+    >>> current_subsequence = []
+    >>> create_state_space_tree(sequence, current_subsequence, 0)
+    []
+    [4]
+    [3]
+    [3, 4]
+    [2]
+    [2, 4]
+    [2, 3]
+    [2, 3, 4]
+    [1]
+    [1, 4]
+    [1, 3]
+    [1, 3, 4]
+    [1, 2]
+    [1, 2, 4]
+    [1, 2, 3]
+    [1, 2, 3, 4]
     """
 
     if index == len(sequence):
@@ -35,7 +85,7 @@ def create_state_space_tree(
 
 
 if __name__ == "__main__":
-    seq: list[Any] = [3, 1, 2, 4]
+    seq: list[Any] = [1, 2, 3]
     generate_all_subsequences(seq)
 
     seq.clear()