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Welcome back.

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In this video, let's get started with another interesting coding interview question, which is called

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the longest palindromic subsequence question.

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The question reads given a string s, find the longest palindromic subsequence length in S, so we are

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asked to find the length of the longest palindromic subsequence in a string, which is given to us,

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and the question then goes on to define what a subsequence is.

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So a subsequence is a sequence that can be derived from another sequence by deleting some or no elements

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without changing the order of the remaining elements.

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Okay, and then it says string s will have at least one character.

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So this means that we don't need to explicitly ensure that our code does not fail if we are given a

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string of length zero.

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So that's not going to happen because it's mentioned in the question.

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And again we are also given an example over here.

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If this is the string s which is given to us.

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Notice that if we delete these two characters and we are allowed to delete characters as per the definition

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of a subsequence given over here.

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So if we do that, we are left with a string that is, pee pee pee pee.

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And this is a palindrome of length four.

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And that's why the expected output, if this is the string s given to us, is equal to four.

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So this is the question at hand.

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We will be given a string s, and we have to identify the length of the longest palindromic subsequence

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that we can form from the given string.

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In the next video, let's discuss what approach we can take to solve this question.