# LeetCode 438. Find All Anagrams in a String

## Description

https://leetcode.com/problems/find-all-anagrams-in-a-string/

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 * 104`
• `s` and `p` consist of lowercase English letters.

## Explanation

Iterate the string s with a pointer i and find out all the positions where s[i: i+len(p)] has the same counter as string p.

## Python Solution

``````class Solution:
def findAnagrams(self, s: str, p: str) -> List[int]:
results = []

p_set = collections.Counter(p)
len_p = len(p)

for i in range(len(s) - len_p + 1):
sub = s[i : i + len_p]

if collections.Counter(sub) == p_set:
results.append(i)

return results``````
• Time Complexity: O(N).
• Space Complexity: O(N).