- #1

member 428835

I'm trying to write a code that, given a list of integers, will output the next lexicographic permutation. But my output gives me None, and I can't see why. Is it because I am incorrectly calling the reverse function? Any help is greatly appreciated!

Python:

```
class Solution(object):
def reverse(self, nums, i, j):
while i < j:
nums[I], nums[j] = nums[j], nums
i += 1
j -= 1
def nextPermutation(self, nums):
# Length of the array
n = len(nums)
# Index of the first element that is smaller than
# the element to its right.
index = -1
# Loop from right to left
for i in range(n - 1, 0, -1):
if nums[I] > nums[i - 1]:
index = i - 1
break
# Base condition
if index == -1:
return self.reverse(nums, 0, n - 1)
j = n - 1
# Scan right to left to find first element
# greater than the above find element
for i in range(n - 1, index, -1):
if nums[I] > nums[index]:
j = i
break
# Swap the elements
nums[index], nums[j] = nums[j], nums[index]
# Reverse the elements from index + 1 to the nums.length
newNum = self.reverse(nums, index + 1, n - 1)
return newNum
if __name__ == "__main__":
nums = [1,3,2]
ob1 = Solution()
print(ob1.nextPermutation(nums))
```