Q:
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 <= 1000
s
only consists of letters 'a' and 'b'
A:
就是存入一个list里,然后找第一个 s
consisting only of letters 'a'
and 'b'
. In a single step you can remove one palindromic subsequence from s
.0 <= s.length <= 1000
s
only consists of letters 'a' and 'b'(NOTE: should not use vector, as we need insert at the begining, can use std::deque. or std:list )
class Solution { public: int maximum69Number (int num) { std::list<int> list; while(num>0) { int r = num%10; num /= 10; list.push_front(r); } bool flipped = false; int res = 0; for(auto v:list) { if(v==6 && !flipped) { v = 9; flipped = true; } res = res*10 + v; } return res; } };
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