Given a string s consisting only of letters 'a' and 'b'. In a single step you can remove one palindromic subsequence from s.
Return the minimum number of steps to make the given string empty.
A string is a subsequence of a given string, if it is generated by deleting some characters of a given string without changing its order.
A string is called palindrome if is one that reads the same backward as well as forward.
Example 1:
Input: s = "ababa" Output: 1 Explanation: String is already palindrome
Example 2:
Input: s = "abb" Output: 2 Explanation: "abb" -> "bb" -> "". Remove palindromic subsequence "a" then "bb".
Example 3:
Input: s = "baabb" Output: 2 Explanation: "baabb" -> "b" -> "". Remove palindromic subsequence "baab" then "b".
Example 4:
Input: s = "" Output: 0
Constraints:
0 <= s.length <= 1000sonly consists of letters ‘a’ and ‘b’
Solution: Math
if s is empty => 0 step
if s is a palindrome => 1 step
Otherwise, 2 steps…
1. delete all the as
2. delete all the bs
Time complexity: O(n)
Space complexity: O(n) / O(1)
C++
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// Author: Huahua class Solution { public: int removePalindromeSub(string s) { if (s.empty()) return 0; if (s == string(rbegin(s), rend(s))) return 1; return 2; } }; |
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