chore(Python): add find all permutations (#831)

* added find_all_permutations

* added test case for find_all_permutations

* updated README with find all permutations

* Added desc and time complexity of find_all_permutations

* PR comment spelling correction

algorithms/Python/README.md

@@ -63,6 +63,7 @@
 - [Unique Character](strings/unique_character.py)
 - [Add String](strings/add_string.py)
 - [Rabin Karp algorithm](strings/rabin-karp-algorithm.py)
+- [Find all permutations](strings/find_all_permutations.py)
 
 ## Dynamic Programming
 - [Print Fibonacci Series Up To N-th Term](dynamic_programming/fibonacci_series.py)

algorithms/Python/strings/find_all_permutations.py

@@ -0,0 +1,28 @@
+"""
+Find all the permutations of a given string
+Sample input: 'ABC'
+Expected output: ['ABC', 'ACB', 'BAC', 'BCA', 'CAB', 'CBA']
+Description: The algorithm is recursive. In each recursion, each element of the string (left) is removed and added to the beginning (head). This process is repeated until left is empty.
+Time complexity: (n!)
+"""
+
+def permutation(head, left, permutations):
+    if len(left) == 0:
+        permutations.append(head)
+    else:
+        for i in range(len(left)):
+            permutation(head+left[i], left[:i]+left[i+1:], permutations)
+
+def find_all_permutations(string):
+    permutations = []
+    permutation('', string, permutations)
+    return permutations
+
+if __name__ == "__main__": 
+    input = 'ABC'
+    output = find_all_permutations(input)
+
+    expected = ['ABC', 'ACB', 'BAC', 'BCA', 'CAB', 'CBA']
+    assert len(output) == len(expected), f"Expected 6 permutations, got: {len(expected)}"
+    for perm in expected:
+        assert perm in output, f"Expected permutation {perm} to be in output, missing"