438. Find All Anagrams in a String LeetCode Solution

In this guide, you will get 438. Find All Anagrams in a String LeetCode Solution with the best time and space complexity. The solution to Find All Anagrams in a String problem is provided in various programming languages like C++, Java, and Python. This will be helpful for you if you are preparing for placements, hackathons, interviews, or practice purposes. The solutions provided here are very easy to follow and include detailed explanations.

Table of Contents

1. Problem Statement
2. Complexity Analysis
3. Find All Anagrams in a String solution in C++
4. Find All Anagrams in a String solution in Java
5. Find All Anagrams in a String solution in Python
6. Additional Resources

Problem Statement of 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.

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.

Complexity Analysis

• Time Complexity: O(n)
• Space Complexity: O(26)

438. Find All Anagrams in a String LeetCode Solution in C++

class Solution {
 public:
  vector<int> findAnagrams(string s, string p) {
    vector<int> ans;
    vector<int> count(128);
    int required = p.length();

    for (const char c : p)
      ++count[c];

    for (int l = 0, r = 0; r < s.length(); ++r) {
      if (--count[s[r]] >= 0)
        --required;
      while (required == 0) {
        if (r - l + 1 == p.length())
          ans.push_back(l);
        if (++count[s[l++]] > 0)
          ++required;
      }
    }

    return ans;
  }
};
/* code provided by PROGIEZ */

438. Find All Anagrams in a String LeetCode Solution in Java

class Solution {
  public List<Integer> findAnagrams(String s, String p) {
    List<Integer> ans = new ArrayList<>();
    int[] count = new int[128];
    int required = p.length();

    for (final char c : p.toCharArray())
      ++count[c];

    for (int l = 0, r = 0; r < s.length(); ++r) {
      if (--count[s.charAt(r)] >= 0)
        --required;
      while (required == 0) {
        if (r - l + 1 == p.length())
          ans.add(l);
        if (++count[s.charAt(l++)] > 0)
          ++required;
      }
    }

    return ans;
  }
}
// code provided by PROGIEZ

438. Find All Anagrams in a String LeetCode Solution in Python

class Solution:
  def findAnagrams(self, s: str, p: str) -> list[int]:
    ans = []
    count = collections.Counter(p)
    required = len(p)

    for r, c in enumerate(s):
      count[c] -= 1
      if count[c] >= 0:
        required -= 1
      if r >= len(p):
        count[s[r - len(p)]] += 1
        if count[s[r - len(p)]] > 0:
          required += 1
      if required == 0:
        ans.append(r - len(p) + 1)

    return ans
 # code by PROGIEZ

Additional Resources

• Explore all LeetCode problem solutions at Progiez here
• Explore all problems on LeetCode website here

Happy Coding! Keep following PROGIEZ for more updates and solutions.