809. Expressive Words LeetCode Solution | Easy Approach

Minimum Cost to Merge Stones

Expressive Words Sometimes people repeat letters to represent extra feeling. For example:

  • "hello" -> "heeellooo"
  • "hi" -> "hiiii"

In these strings like "heeellooo", we have groups of adjacent letters that are all the same: "h""eee""ll""ooo".

You are given a string s and an array of query strings words. A query word is stretchy if it can be made to be equal to s by any number of applications of the following extension operation: choose a group consisting of characters c, and add some number of characters c to the group so that the size of the group is three or more.

  • For example, starting with "hello", we could do an extension on the group "o" to get "hellooo", but we cannot get "helloo" since the group "oo" has a size less than three. Also, we could do another extension like "ll" -> "lllll" to get "helllllooo". If s = "helllllooo", then the query word "hello" would be stretchy because of these two extension operations: query = "hello" -> "hellooo" -> "helllllooo" = s.

Return the number of query strings that are stretchy.

Example 1:

Input: s = "heeellooo", words = ["hello", "hi", "helo"]
Output: 1
We can extend "e" and "o" in the word "hello" to get "heeellooo".
We can't extend "helo" to get "heeellooo" because the group "ll" is not size 3 or more.

Example 2:

Input: s = "zzzzzyyyyy", words = ["zzyy","zy","zyy"]
Output: 3


  • 1 <= s.length, words.length <= 100
  • 1 <= words[i].length <= 100
  • s and words[i] consist of lowercase letters.

Expressive Words Solutions

Time: O(n)
Space: O(n)


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