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1003. Check If Word Is Valid After Substitutions

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Description

We are given that the string "abc" is valid.

From any valid string V, we may split V into two pieces X and Y such that X + Y (X concatenated with Y) is equal to V.  (X or Y may be empty.)  Then, X + "abc" + Y is also valid.

If for example S = "abc", then examples of valid strings are: "abc", "aabcbc", "abcabc", "abcabcababcc".  Examples of invalid strings are: "abccba", "ab", "cababc", "bac".

Return true if and only if the given string S is valid.

 

Example 1:

Input: "aabcbc"

Output: true

Explanation: 

We start with the valid string "abc".

Then we can insert another "abc" between "a" and "bc", resulting in "a" + "abc" + "bc" which is "aabcbc".

Example 2:

Input: "abcabcababcc"

Output: true

Explanation: 

"abcabcabc" is valid after consecutive insertings of "abc".

Then we can insert "abc" before the last letter, resulting in "abcabcab" + "abc" + "c" which is "abcabcababcc".

Example 3:

Input: "abccba"

Output: false

Example 4:

Input: "cababc"

Output: false

 

Note:

1. 1 <= S.length <= 20000
2. S[i] is 'a', 'b', or 'c'

 

Solutions

Python3

Java

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