[mypy] Fix type annotations for strings (#4641)

* Fix mypy error for min_cost_string_conversion.py

* Fix mypy error for manacher.py

* Fix mypy error for aho_corasick.py

strings/aho_corasick.py

@@ -3,8 +3,8 @@ from typing import Dict, List, Union
 
 
 class Automaton:
-    def __init__(self, keywords: List[str]):
-        self.adlist = list()
+    def __init__(self, keywords: list[str]):
+        self.adlist: list[dict] = list()
         self.adlist.append(
             {"value": "", "next_states": [], "fail_state": 0, "output": []}
         )
@@ -22,9 +22,8 @@ class Automaton:
     def add_keyword(self, keyword: str) -> None:
         current_state = 0
         for character in keyword:
-            if self.find_next_state(current_state, character):
-                current_state = self.find_next_state(current_state, character)
-            else:
+            next_state = self.find_next_state(current_state, character)
+            if next_state is None:
                 self.adlist.append(
                     {
                         "value": character,
@@ -35,10 +34,12 @@ class Automaton:
                 )
                 self.adlist[current_state]["next_states"].append(len(self.adlist) - 1)
                 current_state = len(self.adlist) - 1
+            else:
+                current_state = next_state
         self.adlist[current_state]["output"].append(keyword)
 
     def set_fail_transitions(self) -> None:
-        q = deque()
+        q: deque = deque()
         for node in self.adlist[0]["next_states"]:
             q.append(node)
             self.adlist[node]["fail_state"] = 0
@@ -68,7 +69,9 @@ class Automaton:
         >>> A.search_in("whatever, err ... , wherever")
         {'what': [0], 'hat': [1], 'ver': [5, 25], 'er': [6, 10, 22, 26]}
         """
-        result = dict()  # returns a dict with keywords and list of its occurrences
+        result: dict = (
+            dict()
+        )  # returns a dict with keywords and list of its occurrences
         current_state = 0
         for i in range(len(string)):
             while (
@@ -76,10 +79,11 @@ class Automaton:
                 and current_state != 0
             ):
                 current_state = self.adlist[current_state]["fail_state"]
-            current_state = self.find_next_state(current_state, string[i])
-            if current_state is None:
+            next_state = self.find_next_state(current_state, string[i])
+            if next_state is None:
                 current_state = 0
             else:
+                current_state = next_state
                 for key in self.adlist[current_state]["output"]:
                     if not (key in result):
                         result[key] = []

strings/manacher.py

@@ -35,27 +35,28 @@ def palindromic_string(input_string: str) -> str:
     length = [1 for i in range(len(new_input_string))]
 
     # for each character in new_string find corresponding palindromic string
-    for i in range(len(new_input_string)):
-        k = 1 if i > r else min(length[l + r - i] // 2, r - i + 1)
+    start = 0
+    for j in range(len(new_input_string)):
+        k = 1 if j > r else min(length[l + r - j] // 2, r - j + 1)
         while (
-            i - k >= 0
-            and i + k < len(new_input_string)
-            and new_input_string[k + i] == new_input_string[i - k]
+            j - k >= 0
+            and j + k < len(new_input_string)
+            and new_input_string[k + j] == new_input_string[j - k]
         ):
             k += 1
 
-        length[i] = 2 * k - 1
+        length[j] = 2 * k - 1
 
         # does this string is ending after the previously explored end (that is r) ?
         # if yes the update the new r to the last index of this
-        if i + k - 1 > r:
-            l = i - k + 1  # noqa: E741
-            r = i + k - 1
+        if j + k - 1 > r:
+            l = j - k + 1  # noqa: E741
+            r = j + k - 1
 
         # update max_length and start position
-        if max_length < length[i]:
-            max_length = length[i]
-            start = i
+        if max_length < length[j]:
+            max_length = length[j]
+            start = j
 
     # create that string
     s = new_input_string[start - max_length // 2 : start + max_length // 2 + 1]

strings/min_cost_string_conversion.py

@@ -1,5 +1,3 @@
-from typing import List, Tuple
-
 """
 Algorithm for calculating the most cost-efficient sequence for converting one string
 into another.
@@ -18,7 +16,7 @@ def compute_transform_tables(
     replace_cost: int,
     delete_cost: int,
     insert_cost: int,
-) -> Tuple[List[int], List[str]]:
+) -> tuple[list[list[int]], list[list[str]]]:
     source_seq = list(source_string)
     destination_seq = list(destination_string)
     len_source_seq = len(source_seq)
@@ -28,7 +26,7 @@ def compute_transform_tables(
         [0 for _ in range(len_destination_seq + 1)] for _ in range(len_source_seq + 1)
     ]
     ops = [
-        [0 for _ in range(len_destination_seq + 1)] for _ in range(len_source_seq + 1)
+        ["0" for _ in range(len_destination_seq + 1)] for _ in range(len_source_seq + 1)
     ]
 
     for i in range(1, len_source_seq + 1):
@@ -59,7 +57,7 @@ def compute_transform_tables(
     return costs, ops
 
 
-def assemble_transformation(ops: List[str], i: int, j: int) -> List[str]:
+def assemble_transformation(ops: list[list[str]], i: int, j: int) -> list[str]:
     if i == 0 and j == 0:
         return []
     else: