Is Find All Anagrams in a String easy or hard?

Find All Anagrams in a String is generally classified as a medium-level problem. The main challenge is recognizing the sliding window pattern and managing character frequency updates efficiently.

Find All Anagrams in a String Python/Java solution

Python solutions typically use a list of size 26 for character counts and implement a sliding window across the string. Java solutions often use either integer arrays or HashMap-based frequency tracking with two pointers. Both approaches achieve O(n) time complexity.

How to solve Find All Anagrams in a String in O(n)?

Use a sliding window of size equal to the pattern length and maintain character frequency counts for both the pattern and the current window. Move the window one step at a time, updating counts for entering and leaving characters. When both frequency counts match, record the starting index. This processes the string in a single pass.

What is the best approach for Find All Anagrams in a String?

The sliding window with character frequency counting is the most efficient approach. Maintain a window of length equal to the pattern and update counts as the window moves across the string. Matching frequency arrays indicate an anagram. This runs in O(n) time with O(1) extra space for fixed alphabets.

Is Find All Anagrams in a String asked at Google/Amazon/Meta?

Find All Anagrams in a String is a common interview problem at large tech companies including Amazon, Meta, and Google. It tests understanding of sliding window techniques, frequency counting, and efficient substring processing.

What data structure is used in Find All Anagrams in a String?

The main data structures are frequency arrays or hash maps that store character counts. These structures allow constant-time updates and comparisons while the sliding window moves across the string.

What is the time complexity of Find All Anagrams in a String?

The optimal solution runs in O(n) time, where n is the length of the string. Each character is processed once as the sliding window expands and contracts. Frequency updates and comparisons are constant time when using a fixed-size array.

Description Solution Video 12:14

438. Find All Anagrams in a String

Medium54.7% acceptance15 companies

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.

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: