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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:
"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: true Explanation: "" -> "abc" -> "aabcbc" Thus, "aabcbc" is valid.
Example 2:
Input: s = "abcabcababcc" Output: true Explanation: "" -> "abc" -> "abcabc" -> "abcabcabc" -> "abcabcababcc" 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'
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