The idea is very straightforward: if you can make s non-winnable by a move, then you will win.
Write a function to determine if the starting player can guarantee a win.
If you are interested to learn more, this post shares a more sophisticated solution using game theory (it reduces the running time to 0 seconds!). The code is restructured as below.
You are playing the following Flip Game with your friend: Given a string that contains only these two characters:
-, you and your friend take turns to flip two consecutive
"--". The game ends when a person can no longer make a move and therefore the other person will be the winner.
The simplest solution that I have found is here (refer to the first paragraph for explanations of the idea and the Java code). I rewrite it in C++.
Derive your algorithm's runtime complexity.
For example, given
s = "++++", return true. The starting player can guarantee a win by flipping the middle
"++" to become