permutation_in_string

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567. Permutation in String (Medium)

Given two strings s1 and s2, write a function to return true if s2 contains the permutation of s1. In other words, one of the first string's permutations is the substring of the second string.

 

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

 

Note:

1. The input strings only contain lower case letters.
2. The length of both given strings is in range [1, 10,000].

Related Topics

[Two Pointers] [Sliding Window]

Similar Questions

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

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?