556. Next Greater Element III

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跟前天的这道题基本一模一样，ctrl+c/v...

31. Next Permutation

smallest great --> 基本思路是找到能改大的最小digit

1. 因为是最小digit，从右往左找

2. 用的数字不能变，所以「改大」就是能和自己右侧较大数字交换位置

class Solution:
    def nextGreaterElement(self, n: int) -> int:
        nums = [str(n)[x] for x in range(len(str(n)))]
        i = len(nums)-1
        while i > 0:
            if nums[i-1] >= nums[i]:
                i -= 1
            else:
                pivot = i
                while pivot < len(nums)-1:
                    if nums[pivot+1] <= nums[i-1]: break
                    pivot += 1
                nums[i-1], nums[pivot] = nums[pivot], nums[i-1]
                nums[i:] = nums[i:][::-1] # 倒转list切片，这个值得记忆一下...
                break
        
        res = int(''.join(nums))
        
        if i == 0 or res>2**31-1:
            return -1

        return res