Next permutation

题目描述

解题方法

Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.

If such arrangement is not possible, it must rearrange it as the lowest possible order (ie, sorted in ascending order).

The replacement must be in-place, do not allocate extra memory.

Here are some examples. Inputs are in the left-hand column and its corresponding outputs are in the right-hand column.

1,2,3 → 1,3,2
3,2,1 → 1,2,3
1,1,5 → 1,5,1

Solution

• 从右往左找，找到第一个非递增的数，这里记为k
• 从k往右边找，找到比它大的最小的数,几位p
• 将k和p swap, 然后再将现在p的右边的数字ascending sort一下

注意点：

• 完全descending的情况，说明已经是最大值
• reverse的写法，（因为右边其实已经是descending了）

Reference