Description
Given a positive integer n, find the smallest integer which has exactly the same digits existing in the integer n and is greater in value than n. If no such positive integer exists, return -1.
Note that the returned integer should fit in 32-bit integer, if there is a valid answer but it does not fit in 32-bit integer, return -1.
Example 1:
Input: n = 12 Output: 21
Example 2:
Input: n = 21 Output: -1
Constraints:
1 <= n <= 231 - 1
Solution
Python3
class Solution:
def nextGreaterElement(self, n: int) -> int:
s = list(str(n))
i = len(s) - 2
while i >= 0 and s[i] >= s[i+1]:
i -= 1
if i < 0: return -1
j = len(s) - 1
while s[j] <= s[i]:
j -= 1
s[i],s[j] = s[j],s[i]
s[i+1:] = reversed(s[i+1:])
res = int("".join(s))
return res if res < (1 << 31) else -1