Leetcode 1003. Check If Word Is Valid After Substitutions

Given a string s, determine if it is valid.

A string s is valid if, starting with an empty string t = "", you can transform t into s after performing the following operation any number of times:

• Insert string "abc" into any position in t. More formally, t becomes tleft + "abc" + tright, where t == tleft + tright. Note that tleft and tright may be empty.

Return true if s is a valid string, otherwise, return false.

Example 1:

Input: s = "aabcbc"Output: trueExplanation:"" -> "abc" -> "aabcbc" Thus, "aabcbc" is valid.

Example 2:

Input: s = "abcabcababcc"Output: trueExplanation:"" -> "abc" -> "abcabc" -> "abcabcabc" -> "abcabcababcc" Thus, "abcabcababcc" is valid.

Example 3:

Input: s = "abccba"Output: falseExplanation: It is impossible to get "abccba" using the operation.

Constraints:

• 1 <= s.length <= 2 * 104

• s consists of letters 'a', 'b', and 'c'

能过就行，不强求了。

Runtime: 635 ms, faster than 5.13% of Java online submissions for Check If Word Is Valid After Substitutions.

Memory Usage: 43 MB, less than 21.79% of Java online submissions for Check If Word Is Valid After Substitutions.