Elimination Game问题及解法

问题描述：

There is a list of sorted integers from 1 to n. Starting from left to right, remove the first number and every other number afterward until you reach the end of the list.

Repeat the previous step again, but this time from right to left, remove the right most number and every other number from the remaining numbers.

We keep repeating the steps again, alternating left to right and right to left, until a single number remains.

Find the last number that remains starting with a list of length n.

示例:

Input:n = 9,1 2 3 4 5 6 7 8 92 4 6 82 66Output:6

问题分析：

通过分析，我们可以找到其中消除的规律，从消除的第二行开始，每次记录好最左侧的元素值，直到最后剩余一个元素，那么这个最左侧元素值即为答案。

过程详见代码：

class Solution {public:    int lastRemaining(int n) {       if (n == 1) return 1;if (n <= 3) return 2;int row = 1, left = 2, num = n / 2;while (num > 1){if (row % 2 == 1){if(num % 2 == 1) left = left + (int)pow(2,row);}else{left = left + (int)pow(2, row);}row++;num = num / 2;}return left;    }};