Backtracking

public boolean canWin(String s) {
if(s==null||s.length()==0){
return false;
}
return canWinHelper(s.toCharArray());
}
public boolean canWinHelper(char[] arr){
for(int i=0; i<arr.length-1;i++){
if(arr[i]==’+’&&arr[i+1]==’+’){
arr[i]=’-’;
arr[i+1]=’-’;
boolean win = canWinHelper(arr);
arr[i]=’+’;
arr[i+1]=’+’;
play wins
if(!win){
return true;
}
}
}
return false;
}