Is Next Greater Element III easy or hard?

Next Greater Element III is considered a Medium difficulty problem. The implementation itself is short, but recognizing that the task is equivalent to the next lexicographical permutation problem requires algorithmic insight.

Next Greater Element III Python/Java solution

Python and Java implementations follow the same steps: convert the integer to a character or digit array, apply the next permutation logic, then reconstruct the integer and check the 32-bit limit. The logic remains identical across languages with only syntax differences.

How to solve Next Greater Element III in O(n)?

Scan the digits from right to left to find the first index i where digits[i] < digits[i+1]. Then find the smallest digit greater than digits[i] to its right and swap them. Finally reverse the digits after index i so the suffix becomes the smallest possible order. This sequence of operations produces the next lexicographically greater permutation in linear time.

What is the best approach for Next Greater Element III?

The optimal approach is the Next Permutation algorithm. Convert the integer to a digit array, find the pivot where digits stop increasing from right to left, swap it with the smallest larger digit in the suffix, then reverse the suffix. This produces the smallest number greater than the original using the same digits in O(n) time and O(1) space.

Is Next Greater Element III asked at Google/Amazon/Meta?

Variants of permutation and next greater element problems frequently appear in interviews at companies like Google, Amazon, and Meta. The question tests understanding of permutations, greedy digit manipulation, and in-place array transformations.

What data structure is used in Next Greater Element III?

The algorithm typically converts the integer into an array or string of digits so it can be manipulated like a sequence. Operations involve scanning, swapping elements, and reversing a suffix, which are standard array or string manipulation techniques.

What is the time complexity of Next Greater Element III?

The optimal solution runs in O(n) time where n is the number of digits. The algorithm performs a few linear passes: finding the pivot, locating the next larger digit, and reversing the suffix. Space complexity remains O(1) since all operations are done in place on the digit array.

Description Solution Video 35:10

556. Next Greater Element III

Q: What is the best approach for Next Greater Element III?

The optimal approach is the Next Permutation algorithm. Convert the integer to a digit array, find the pivot where digits stop increasing from right to left, swap it with the smallest larger digit in the suffix, then reverse the suffix. This produces the smallest number greater than the original using the same digits in O(n) time and O(1) space.

Q: Is Next Greater Element III asked at Google/Amazon/Meta?

Variants of permutation and next greater element problems frequently appear in interviews at companies like Google, Amazon, and Meta. The question tests understanding of permutations, greedy digit manipulation, and in-place array transformations.

Q: What data structure is used in Next Greater Element III?

The algorithm typically converts the integer into an array or string of digits so it can be manipulated like a sequence. Operations involve scanning, swapping elements, and reversing a suffix, which are standard array or string manipulation techniques.

Q: What is the time complexity of Next Greater Element III?

The optimal solution runs in O(n) time where n is the number of digits. The algorithm performs a few linear passes: finding the pivot, locating the next larger digit, and reversing the suffix. Space complexity remains O(1) since all operations are done in place on the digit array.

Medium35.2% acceptance11 companies

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: