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567. Permutation in String (Medium)

Given two strings s1 and s2, return true if s2 contains a permutation of s1, or false otherwise.

In other words, return true if one of s1's permutations is the substring of s2.

 

Example 1:

Input: s1 = "ab", s2 = "eidbaooo"
Output: true
Explanation: s2 contains one permutation of s1 ("ba").

Example 2:

Input: s1 = "ab", s2 = "eidboaoo"
Output: false

 

Constraints:

• 1 <= s1.length, s2.length <= 104
• s1 and s2 consist of lowercase English letters.

Related Topics

[Hash Table] [Two Pointers] [String] [Sliding Window]

Similar Questions

1. Minimum Window Substring (Hard)
2. Find All Anagrams in a String (Medium)

Hints

Hint 1

Obviously, brute force will result in TLE. Think of something else.

Hint 2

How will you check whether one string is a permutation of another string?

Hint 3

One way is to sort the string and then compare. But, Is there a better way?

Hint 4

If one string is a permutation of another string then they must one common metric. What is that?

Hint 5

Both strings must have same character frequencies, if one is permutation of another. Which data structure should be used to store frequencies?

Hint 6

What about hash table? An array of size 26?