leetcode 390. 消除游戏( java& python3)

生日第一件事 核酸

生日第二件事 吃饭

生日第三件事 每日一题 

java：

官方题解思路（下面截图）谢谢～等差数列模拟

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class Solution {
    public int lastRemaining(int n) {
        int first = 1, end = n;
        int sum = n, k = 0, step = 1;
        while(sum > 1){
            if (k % 2 == 0) {
                first = first + step;
                end = (sum % 2 == 0) ? end : end - step;
            } else {
                first = (sum % 2 == 0) ? first : first + step;
                end = end-step;
            }
            k ++;
            sum = sum >> 1;
            step = step << 1;
        }
        return first;
    }
}

python3:

class Solution:
    def lastRemaining(self, n: int) -> int:
        a1 = 1
        k, cnt, step = 0, n, 1
        while cnt > 1:
            if k % 2 == 0:  
                a1 += step
            else:  
                if cnt % 2:
                    a1 += step
            k += 1
            cnt >>= 1
            step <<= 1
        return a1