You are given a string s consisting of n characters which are either 'X' or 'O'.
A move is defined as selecting three consecutive characters of s and converting them to 'O'. Note that if a move is applied to the character 'O', it will stay the same.
Return the minimum number of moves required so that all the characters of s are converted to 'O'.
Example 1:
Input: s = "XXX" Output: 1 Explanation: XXX -> OOO We select all the 3 characters and convert them in one move.
Example 2:
Input: s = "XXOX" Output: 2 Explanation: XXOX -> OOOX -> OOOO We select the first 3 characters in the first move, and convert them to'O'. Then we select the last 3 characters and convert them so that the final string contains all'O's.
Example 3:
Input: s = "OOOO" Output: 0 Explanation: There are no'X'sinsto convert.
Constraints:
3 <= s.length <= 1000s[i]is either'X'or'O'.
Solution: Straight Forward
if s[i] == ‘X’, change s[i], s[i + 1] and s[i + 2] to ‘O’.
Time complexity: O(n)
Space complexity: O(1)
C++
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class Solution { public: int minimumMoves(string s) { const int n = s.length(); int ans = 0; for (size_t i = 0; i < n; ++i) { if (s[i] == 'X') { ans += 1; i += 2; } } return ans; } }; |