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 int
. More formally,t
becomestleft + "abc" + tright
, wheret == tleft + tright
. Note thattleft
andtright
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.
Constraints:
-
1 <= s.length <= 2 * 104
-
s
consists of letters'a'
,'b'
, and'c'
SOLUTION:
class Solution:
def isValid(self, s: str) -> bool:
while "abc" in s:
i = s.index("abc")
s = s[:i] + s[i+3:]
return s == ""
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