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Description：
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.
Example:
Input: 4
Output: false
Explanation: 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.
题意：有一堆一定数量的石头，双方每次可以轮流区1-3颗，哪一方先取到最后一颗石头，哪一方获胜；现在要求计算，当你是先手时是否可以胜利；
解法：Nim是博弈论中的经典问题；对于这道题目来说，我们记石头的数量为n；
- 如果n <= 3，那么我们一定可以获胜
- 如果n == 4，那么无论我们取1, 2或者3颗都无法获胜；因此，为了保证我们可以获胜，需要避免当轮到我们取时石头数量为4
- 同理，当n=[5,6,7]时，我们可以获胜
- 如果n == 8，无论我们取1,2或者3颗，都无法确保当下次轮到我们时石头数量为4
综上所述，我们只需要判断石头的数量是否为4的倍数即可知道能否获胜；
Java
class Solution {
public boolean canWinNim(int n) {
return n % 4 == 0 ? false : true;
}
}