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Each line of the input gives a separate data set as a sequence of numbers separated by spaces. The first number on each line gives the number, N, of pancakes in the data set. The input ends when N is 0 (zero) with no other data on the line. The remainder of the data set are the numbers 1 through N in some order giving the initial pancake stack. The numbers indicate the relative sizes of the pancakes. N will be, at most, 30.
For each data set, the output is a single-space separated sequence of numbers on a line. The first number on each line, K, gives the number of flips required to sort the pancakes. This number is followed by a sequence of K numbers, each of which gives the number of pancakes to flip on the corresponding sorting step. There may be several correct solutions for some datasets. For instance 3 3 2 3 is also a solution to the first problem below.
2 2 1 6 2 5 6 1 3 4 0
1 2 4 3 6 4 2
关于Pancake sorting的一种简单情况。就是有种方法可以保证至多2n-3次完成。 类似于选择排序： 先找出n各数字种最大的一个数n，假设所在位置为sn，那么先翻转前sn个数字f(sn)， 使得n在最顶部，之后再翻转前n个元素f(n)，这样一来n就到了最底部。就是两次翻转。 之后再选择第二大的假设为n-1，位置在sn-1，那么先翻转前sn-1个数字f(sn-1)，使得n-1在最 顶部，之后再翻转前n-1个元素f(n-1)，这样一来n-1就到了倒数第二个。也是两次翻转。 注意：每次对于第x大的元素要判断它是不是在倒是第x个位置上，若在就不用翻转这个数字了。 一直进行n-2次，最多2n-4次翻转。剩下上面三个最小的1,2其它的都排序了。 分成2种情况，顶多1次搞定： 12：已经有序，不用翻转。 21：一次，f(2)
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