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 "+--+".
Code is from: https://discuss.leetcode.com/topic/27287/short-java-ruby?show=64350
1 public boolean canWin(String s) { 2 for (int i=-1; (i = s.indexOf("++", i+1)) >= 0; ) 3 if (!canWin(s.substring(0, i) + "-" + s.substring(i + 2))) return true; 4 return false; 5 }
原文：http://www.cnblogs.com/beiyeqingteng/p/5720056.html