Leetcode 292. Nim Game

You are playing the following Nim Game with your friend: There is a heap of stones on the table, each time one of you take turns to remove 1 to 3 stones. The one who removes the last stone will be the winner. You will take the first turn to remove the stones.

Both of you are very clever and have optimal strategies for the game. Write a function to determine whether you can win the game given the number of stones in the heap.

For example, if there are 4 stones in the heap, then you will never win the game: no matter 1, 2, or 3 stones you remove, the last stone will always be removed by your friend.

博弈问题，每次拿1-3个石子，先手，最后拿完的人赢。

4个石子先手的人必输，那么我们先手的情况下，只要石子不是4的倍数就能赢。

class Solution {
public:
    bool canWinNim(int n) {
        return n % 4 ? true : false;
    }
};