Leetcode #2165: Smallest Value of the Rearranged Number
In this guide, we solve Leetcode #2165 Smallest Value of the Rearranged Number in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
You are given an integer num. Rearrange the digits of num such that its value is minimized and it does not contain any leading zeros.
Quick Facts
- Difficulty: Medium
- Premium: No
- Tags: Math, Sorting
Intuition
Sorting reveals structure that is hard to see in the original order.
Once sorted, a linear scan is usually enough to compute the answer.
Approach
Sort the data and sweep through it while maintaining a small state.
This keeps the logic straightforward and reliable.
Steps:
- Sort the data.
- Scan in order while maintaining state.
- Update the best answer.
Example
Input: num = 310
Output: 103
Explanation: The possible arrangements for the digits of 310 are 013, 031, 103, 130, 301, 310.
The arrangement with the smallest value that does not contain any leading zeros is 103.
Python Solution
class Solution:
def smallestNumber(self, num: int) -> int:
neg = num < 0
num = abs(num)
cnt = [0] * 10
while num:
cnt[num % 10] += 1
num //= 10
ans = 0
if neg:
for i in reversed(range(10)):
for _ in range(cnt[i]):
ans *= 10
ans += i
return -ans
if cnt[0]:
for i in range(1, 10):
if cnt[i]:
ans = i
cnt[i] -= 1
break
for i in range(10):
for _ in range(cnt[i]):
ans *= 10
ans += i
return ans
Complexity
The time complexity is , where is the size of the number . The space complexity is .
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.