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 transformt intos 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 ifs is a valid string, otherwise, return false.

Example 1:

Input: s = "aabcbc"
Output: true
Explanation:
"" -> " _abc_ " -> "a _abc_ bc"
Thus, "aabcbc" is valid.

Example 2:

Input: s = "abcabcababcc"
Output: true
Explanation:
"" -> " _abc_ " -> "abc _abc_ " -> "abcabc _abc_ " -> "abcabcab _abc_ c"
Thus, "abcabcababcc" is valid.

Example 3:

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

Example 4:

Input: s = "cababc"
Output: false
Explanation: It is impossible to get "cababc" using the operation.

Constraints:

• 1 <= s.length <= 2 * 104
• s consists of letters 'a', 'b', and 'c'

# @lc code=start
using LeetCode

function is_valid_abc_str(s::String)
    while occursin("abc", s)
        s = replace(s, "abc" => "")
    end
    return s == ""
end
# @lc code=end

is_valid_abc_str (generic function with 1 method)

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