[LeetCode] Flip Game II

Problem Description:

You are playing the following Flip Game with your friend: Given a string that contains only these two characters: + and -, you and your friend take turns to flip two consecutive "++" into "--". The game ends when a person can no longer make a move and therefore the other person will be the winner.

Write a function to determine if the starting player can guarantee a win.

For example, given s = "++++", return true. The starting player can guarantee a win by flipping the middle "++" to become "+--+".

Follow up:
Derive your algorithm‘s runtime complexity.

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++.

The idea is very straightforward: if you can make s non-winnable by a move, then you will win.

1 class Solution {
2 public:
3     bool canWin(string s) {
4         for (int i = -1; (i = s.find("++", i + 1)) >= 0; )
5             if (!canWin(s.substr(0, i) + ‘-‘ + s.substr(i+2)))
6                 return true;
7         return false;
8     }
9 };

[LeetCode] Flip Game II

原文：http://www.cnblogs.com/jcliBlogger/p/4886741.html