31 Next Permutations【M】【19】

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

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算的还是挺麻烦的，用最naive的方法做的。。。理论上应该还有更棒的。。。。。。

class Solution(object):    def nextPermutation(self, nums):        t = 0        a = nums[:]        a.sort(reverse = True)        if a[:] == nums[:]:            nums.reverse()            return        l = len(nums)        if l == 1:# or nums == nums[::-1]:            return        t = l - 1        while t >= 0 and nums[t] > nums[t-1]:            t -= 1        if l - t > 1:            nums[l-1],nums[l-2] = nums[l-2],nums[l-1]            return        if t == l - 1:            while t > 0 and nums[t] <= nums[t-1]:                t -= 1            a = nums[t-1:l][::-1]            a.sort()            pos = a.index(nums[t-1],0,len(a)) + 1            while a[pos] == a[pos - 1]:                pos += 1            nums[t-1] = a[pos]            del a[pos]            nums[t:l] = a[:]            return