diff --git a/DIRECTORY.md b/DIRECTORY.md
index a8d00f6cb..6a3d31709 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -552,6 +552,8 @@
   * Problem 12
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_12/sol1.py)
     * [Sol2](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_12/sol2.py)
+  * Problem 120
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_120/sol1.py)
   * Problem 13
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_13/sol1.py)
   * Problem 14
@@ -597,7 +599,7 @@
   * Problem 29
     * [Solution](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_29/solution.py)
   * Problem 30
-    * [Soln](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_30/soln.py)
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_30/sol1.py)
   * Problem 31
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_31/sol1.py)
     * [Sol2](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_31/sol2.py)
diff --git a/strings/aho_corasick.py b/strings/aho_corasick.py
index bb6955bdd..b959dbd58 100644
--- a/strings/aho_corasick.py
+++ b/strings/aho_corasick.py
@@ -1,8 +1,9 @@
 from collections import deque
+from typing import Dict, List, Union
 
 
 class Automaton:
-    def __init__(self, keywords):
+    def __init__(self, keywords: List[str]):
         self.adlist = list()
         self.adlist.append(
             {"value": "", "next_states": [], "fail_state": 0, "output": []}
@@ -12,13 +13,13 @@ class Automaton:
             self.add_keyword(keyword)
         self.set_fail_transitions()
 
-    def find_next_state(self, current_state, char):
+    def find_next_state(self, current_state: int, char: str) -> Union[int, None]:
         for state in self.adlist[current_state]["next_states"]:
             if char == self.adlist[state]["value"]:
                 return state
         return None
 
-    def add_keyword(self, keyword):
+    def add_keyword(self, keyword: str) -> None:
         current_state = 0
         for character in keyword:
             if self.find_next_state(current_state, character):
@@ -36,7 +37,7 @@ class Automaton:
                 current_state = len(self.adlist) - 1
         self.adlist[current_state]["output"].append(keyword)
 
-    def set_fail_transitions(self):
+    def set_fail_transitions(self) -> None:
         q = deque()
         for node in self.adlist[0]["next_states"]:
             q.append(node)
@@ -61,7 +62,7 @@ class Automaton:
                     + self.adlist[self.adlist[child]["fail_state"]]["output"]
                 )
 
-    def search_in(self, string):
+    def search_in(self, string: str) -> Dict[str, List[int]]:
         """
         >>> A = Automaton(["what", "hat", "ver", "er"])
         >>> A.search_in("whatever, err ... , wherever")
diff --git a/strings/boyer_moore_search.py b/strings/boyer_moore_search.py
index 9d32a6943..a3e6cf614 100644
--- a/strings/boyer_moore_search.py
+++ b/strings/boyer_moore_search.py
@@ -17,14 +17,15 @@ Time Complexity : O(n/m)
     n=length of main string
     m=length of pattern string
 """
+from typing import List
 
 
 class BoyerMooreSearch:
-    def __init__(self, text, pattern):
+    def __init__(self, text: str, pattern: str):
         self.text, self.pattern = text, pattern
         self.textLen, self.patLen = len(text), len(pattern)
 
-    def match_in_pattern(self, char):
+    def match_in_pattern(self, char: str) -> int:
         """finds the index of char in pattern in reverse order
 
         Parameters :
@@ -40,7 +41,7 @@ class BoyerMooreSearch:
                 return i
         return -1
 
-    def mismatch_in_text(self, currentPos):
+    def mismatch_in_text(self, currentPos: int) -> int:
         """
         find the index of mis-matched character in text when compared with pattern
         from last
@@ -58,7 +59,7 @@ class BoyerMooreSearch:
                 return currentPos + i
         return -1
 
-    def bad_character_heuristic(self):
+    def bad_character_heuristic(self) -> List[int]:
         # searches pattern in text and returns index positions
         positions = []
         for i in range(self.textLen - self.patLen + 1):
diff --git a/strings/knuth_morris_pratt.py b/strings/knuth_morris_pratt.py
index 2e5e0c7e7..a205ce37e 100644
--- a/strings/knuth_morris_pratt.py
+++ b/strings/knuth_morris_pratt.py
@@ -1,4 +1,7 @@
-def kmp(pattern, text):
+from typing import List
+
+
+def kmp(pattern: str, text: str) -> bool:
     """
     The Knuth-Morris-Pratt Algorithm for finding a pattern within a piece of text
     with complexity O(n + m)
@@ -33,7 +36,7 @@ def kmp(pattern, text):
     return False
 
 
-def get_failure_array(pattern):
+def get_failure_array(pattern: str) -> List[int]:
     """
     Calculates the new index we should go to if we fail a comparison
     :param pattern:
diff --git a/strings/levenshtein_distance.py b/strings/levenshtein_distance.py
index 9b8793544..54948a966 100644
--- a/strings/levenshtein_distance.py
+++ b/strings/levenshtein_distance.py
@@ -13,7 +13,7 @@ python levenshtein-distance.py
 """
 
 
-def levenshtein_distance(first_word, second_word):
+def levenshtein_distance(first_word: str, second_word: str) -> int:
     """Implementation of the levenshtein distance in Python.
     :param first_word: the first word to measure the difference.
     :param second_word: the second word to measure the difference.
diff --git a/strings/manacher.py b/strings/manacher.py
index 73b31a7be..5476e0683 100644
--- a/strings/manacher.py
+++ b/strings/manacher.py
@@ -1,4 +1,4 @@
-def palindromic_string(input_string):
+def palindromic_string(input_string: str) -> str:
     """
     >>> palindromic_string('abbbaba')
     'abbba'
diff --git a/strings/rabin_karp.py b/strings/rabin_karp.py
index d866b1397..81ca611a7 100644
--- a/strings/rabin_karp.py
+++ b/strings/rabin_karp.py
@@ -4,7 +4,7 @@ alphabet_size = 256
 modulus = 1000003
 
 
-def rabin_karp(pattern, text):
+def rabin_karp(pattern: str, text: str) -> bool:
     """
     The Rabin-Karp Algorithm for finding a pattern within a piece of text
     with complexity O(nm), most efficient when it is used with multiple patterns
@@ -51,7 +51,7 @@ def rabin_karp(pattern, text):
     return False
 
 
-def test_rabin_karp():
+def test_rabin_karp() -> None:
     """
     >>> test_rabin_karp()
     Success.