X-Git-Url: https://wannabe.guru.org/gitweb/?a=blobdiff_plain;f=list_utils.py;h=71630dc9a6fdb4d968f890b2ac4d3b8cb78360d2;hb=a4bf4d05230474ad14243d67ac7f8c938f670e58;hp=b877e381041d32564789232e1bb7329cc04503e6;hpb=444d1e5f3e9a39759079736302e3404018141b02;p=python_utils.git

diff --git a/list_utils.py b/list_utils.py
index b877e38..71630dc 100644
--- a/list_utils.py
+++ b/list_utils.py
@@ -65,7 +65,7 @@ def remove_list_if_one_element(lst: List[Any]) -> Any:
         return lst
 
 
-def population_counts(lst: List[Any]) -> Mapping[Any, int]:
+def population_counts(lst: List[Any]) -> Counter:
     """
     Return a population count mapping for the list (i.e. the keys are
     list items and the values are the number of occurrances of that
@@ -200,9 +200,9 @@ def ngrams(lst: Sequence[Any], n):
         yield lst[i : i + n]
 
 
-def permute(seq: Sequence[Any]):
+def permute(seq: str):
     """
-    Returns all permutations of a sequence; takes O(N^2) time.
+    Returns all permutations of a sequence; takes O(N!) time.
 
     >>> for x in permute('cat'):
     ...     print(x)
@@ -217,11 +217,12 @@ def permute(seq: Sequence[Any]):
     yield from _permute(seq, "")
 
 
-def _permute(seq: Sequence[Any], path):
-    if len(seq) == 0:
+def _permute(seq: str, path: str):
+    seq_len = len(seq)
+    if seq_len == 0:
         yield path
 
-    for i in range(len(seq)):
+    for i in range(seq_len):
         car = seq[i]
         left = seq[0:i]
         right = seq[i + 1 :]
@@ -229,7 +230,9 @@ def _permute(seq: Sequence[Any], path):
         yield from _permute(cdr, path + car)
 
 
-def binary_search(lst: Sequence[Any], target: Any, *, sanity_check=False) -> Tuple[bool, int]:
+def binary_search(
+    lst: Sequence[Any], target: Any, *, sanity_check=False
+) -> Tuple[bool, int]:
     """Performs a binary search on lst (which must already be sorted).
     Returns a Tuple composed of a bool which indicates whether the
     target was found and an int which indicates the index closest to