Sliding Window 6 - Medium - Permutations in a String - JAVA

Coding Interviews - Permutations in a String (LeetCode)
This interview question is commonly asked by companies like Oracle, Amazon, Facebook.
We can use a similar sliding window strategy as discussed in 'Longest Substring with K Distinct Characters'. We can use a HashMap to remember the frequencies of all characters in the given pattern. Our goal will be to match all the characters from this HashMap with a sliding window in the given string.

Time Complexity -
For the above algorithm, the Time Complexity will be O(N+M), where 'N' and 'M' are the number of characters in the pattern string S1 and input string S2.

Space Complexity -
The Space Complexity of the algorithm will be O(N) since in the worst case whole pattern string S1 can have distinct characters which will go into the HashMap.

Link to the videos of Sliding Window playlist

1. Max sum subarray of size k - https://youtu.be/-rji0auUztU
2. Smallest Subarray with a given sum / Minimum Size Subarray Sum - https://youtu.be/wlcioUsBcOA
3. Longest Substring with K Distinct Characters - https://youtu.be/e-1X91PcjsA
4. Longest Substring with distinct (without repeating) Characters - https://youtu.be/QQmavXArQ4M
5. Longest Substring with same letters after replacement - https://youtu.be/uPyRa3bvcCc
6. Permutation in a String - https://youtu.be/YZ9JyvSSQ_g
7. String Anagrams - https://youtu.be/PAq9UtFg_04
8. Minimum window substring - https://youtu.be/71FgTUWNVtw
9. Words Concatenation - https://youtu.be/mIY9saZy4o0

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