Find smallest permutation under constraints

Q: Find smallest permutation under constraints

This question evaluates digit-manipulation and combinatorial permutation skills, along with numeric ordering and representation concerns such as leading zeros and overflow handling in the Coding & Algorithms domain.

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Question

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Given a non-negative integer n, consider its decimal digits as a multiset (digits can repeat).

Return the smallest possible integer that can be formed by rearranging the digits of n , allowing leading zeros (i.e., you are allowed to place 0 at the front; the result is still treated as an integer value).
Follow-up: Given an additional integer lowerBound , return the smallest integer strictly greater than lowerBound that can be formed by rearranging the digits of n . If no such number exists, return an indication such as -1 .

Example

n = 178 : smallest permutation (allow leading zeros) is 178 .
Follow-up: n = 178 , lowerBound = 200 → answer is 718 .

Constraints

You may assume n fits in 32-bit signed integer input, but intermediate permutations may exceed 32-bit; define how you handle overflow (e.g., use 64-bit or strings).

Find smallest permutation under constraints

Quick Overview

Example

Constraints

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