may1899992020

Author: rimijoker

Python/Find All Anagrams in a String Leetcode.py

@@ -0,0 +1,40 @@
+class Solution:
+    def findAnagrams(self, s: str, p: str) -> List[int]:
+		# store results in list
+        indices = []
+		# store lenth of string p since this is reused multiple times
+        length_p = len(p)
+
+		# check if p is longer than s, if yes, return empty list
+        if length_p > len(s):
+            return []
+
+        # create baseline for p by counting the characters in p (26 possible characters)
+		# (similar to storing the counts in a dictionary)
+        counter_p = [0] * 26
+        for c in p:
+			# convert each character to its index by calculating the int value and subtracting 97
+			# a = 97 -> a-97 = 0
+			# b = 98 -> b-97 = 1
+			# etc.
+            counter_p[ord(c) - 97] += 1
+
+        # initialize counter with the first characters
+        counter = [0] * 26
+        for i in range(length_p - 1):
+            counter[ord(s[i]) - 97] += 1
+
+        # enumerate through remaining characters and compare to baseline (counter_p)
+		# use enumerator to get both the index we need for removing the first character and
+		# the character we want to add (we are starting with the first character after the once
+		# that were initialized above (if len(p)=3, we start at the 3rd character)
+        for i, c in enumerate(s[length_p - 1:]):
+			# add current character
+            counter[ord(c) - 97] += 1
+			# compare to baseline
+            if counter_p == counter:
+                indices.append(i)
+			# remove character
+            counter[ord(s[i]) - 97] -= 1
+
+        return indices