LeetCode题目链接

题目：

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.

答案：

public:
    bool canWinNim(int n) {
        if (n < 4) {
            return true;
        }
        
        return n % 4 != 0;
    }
};

解析：

主要是将题意转化一下，很快发现只要是4的倍数，都不可能会赢。（如果对方不蠢的话）。想赢的话，只要将剩下的石头个数保持在4的倍数就可以了。