LeetCode Nim Game

原题链接在这里：https://leetcode.com/problems/nim-game/

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.

题解：

列出前几个数，发现只要是四的倍数就return false, 其他都是return true.

Time Complexity: O(1). Space: O(1).

AC Java:

public class Solution {
    public boolean canWinNim(int n) {
        if(n < 0){
            throw new IllegalArgumentException("input number can't be smaller than zero.");
        }
        return n % 4 != 0;
    }
}