Hashing-1

group_anagrams.py

@@ -0,0 +1,22 @@
+"""
+time - o(n)
+space - o(n)
+we take each word, sort its letters and store it as the key, and the word becomes
+a value in dictionary
+"""
+
+from typing import List
+
+
+class Solution:
+    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
+        anagram_map = {}
+        for string in strs:
+            string_tuple = tuple(sorted(list(string)))
+            if not string_tuple in anagram_map:
+                anagram_map[string_tuple] = []
+            anagram_map[string_tuple].append(string)
+        result = []
+        for _, value in anagram_map.items():
+            result.append(value)
+        return result

isomorphic_srtings.py

@@ -0,0 +1,21 @@
+"""
+time - o(n)
+space - o(n)
+we map two characters to each other in two separate dicts
+if the pattern does not repeat we return false
+"""
+
+
+class Solution:
+    def isIsomorphic(self, s: str, t: str) -> bool:
+        if len(s) != len(t):
+            return False
+        s_map = {}
+        t_map = {}
+        for i in range(len(s)):
+            if s[i] not in s_map and t[i] not in t_map:
+                s_map[s[i]] = t[i]
+                t_map[t[i]] = s[i]
+            elif s_map.get(s[i]) != t[i] or t_map.get(t[i]) != s[i]:
+                return False
+        return True

word_pattern.py

@@ -0,0 +1,25 @@
+"""
+time - o(n)
+space - o(n)
+same as isomorphic string we link each word and store them as key value
+pairs in two dictionaries (with key and value interchanged) and if the pattern
+does not repeat return false
+"""
+
+
+class Solution:
+    def wordPattern(self, pattern: str, s: str) -> bool:
+        s_list = s.split()
+        if len(s_list) != len(pattern):
+            return False
+        s_map = {}
+        c_map = {}
+        for i in range(len(pattern)):
+            if pattern[i] not in s_map and s_list[i] not in c_map:
+                s_map[pattern[i]] = s_list[i]
+                c_map[s_list[i]] = pattern[i]
+            elif (
+                s_map.get(pattern[i]) != s_list[i] or c_map.get(s_list[i]) != pattern[i]
+            ):
+                return False
+        return True