LeetCode-in-All
438. Find All Anagrams in a String
Medium
Given two strings s and p, return an array of all the start indices of p’s anagrams in s. You may return the answer in any order.
An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.
Example 1:
Input: s = “cbaebabacd”, p = “abc”
Output: [0,6]
Explanation:
The substring with start index = 0 is "cba", which is an anagram of "abc".
The substring with start index = 6 is "bac", which is an anagram of "abc".
Example 2:
Input: s = “abab”, p = “ab”
Output: [0,1,2]
Explanation:
The substring with start index = 0 is "ab", which is an anagram of "ab".
The substring with start index = 1 is "ba", which is an anagram of "ab".
The substring with start index = 2 is "ab", which is an anagram of "ab".
Constraints:
1 <= s.length, p.length <= 3 * 104sandpconsist of lowercase English letters.
Solution
from typing import List
from collections import defaultdict
class Solution:
def findAnagrams(self, s: str, p: str) -> List[int]:
map = [0] * 26
for char in p:
map[ord(char) - ord('a')] += 1
res = []
i, j = 0, 0
while i < len(s):
idx = ord(s[i]) - ord('a')
# add the new character
map[idx] -= 1
# if the length is greater than windows length, pop the left character in the window
if i >= len(p):
map[ord(s[j]) - ord('a')] += 1
j += 1
finish = True
for k in range(26):
# if it is not an anagram of string p
if map[k] != 0:
finish = False
break
if i >= len(p) - 1 and finish:
res.append(j)
i += 1
return res