Is Find The Least Frequent Digit easy or hard?

Find The Least Frequent Digit is typically categorized as an Easy problem. The main idea is straightforward frequency counting, a common beginner-friendly technique used in array, math, and hash table problems.

Find The Least Frequent Digit Python/Java solution

In Python or Java, convert the number to a string or repeatedly extract digits using modulo operations. Maintain a frequency array of size 10, update counts while iterating, and finally scan the array to return the digit with the minimum non-zero frequency. The implementation runs in O(n) time.

How to solve Find The Least Frequent Digit in O(n)?

Traverse the digits once and maintain a frequency array of size 10. Increment the counter for each digit encountered. After the pass, iterate through the array to find the digit with the smallest non-zero frequency. This guarantees O(n) time and constant extra space.

What is the best approach for Find The Least Frequent Digit?

The most efficient approach uses a counting array to track how many times each digit (0–9) appears. Iterate through the digits once to build the frequency table, then scan the table to find the smallest non-zero count. This runs in O(n) time with O(1) space because the digit range is fixed.

Is Find The Least Frequent Digit asked at Google/Amazon/Meta?

Digit frequency and counting problems appear frequently in coding interviews at companies like Amazon, Google, and Meta. While the exact problem title may vary, the underlying concept—tracking frequencies using arrays or hash maps—is a common interview pattern.

What data structure is used in Find The Least Frequent Digit?

A fixed-size array of length 10 is the most common structure because digits range from 0 to 9. Some implementations also use a hash table or map for counting, but an array is faster and uses constant memory.

What is the time complexity of Find The Least Frequent Digit?

The optimal solution runs in O(n) time where n is the number of digits in the input. One pass counts digit frequencies and a second constant-size scan (0–9) finds the minimum frequency. Space complexity remains O(1) due to the fixed-size frequency array.

Description Hints 1 Solution Video 3:45

3663. Find The Least Frequent Digit

Easy68.8% acceptance1 company

Given an integer n, find the digit that occurs least frequently in its decimal representation. If multiple digits have the same frequency, choose the smallest digit.

Return the chosen digit as an integer.

The frequency of a digit x is the number of times it appears in the decimal representation of n.

Example 1:

Input: n = 1553322

Output: 1

Explanation:

The least frequent digit in n is 1, which appears only once. All other digits appear twice.

Example 2:

Input: n = 723344511

Output: 2

Explanation:

The least frequent digits in n are 7, 2, and 5; each appears only once.

Constraints:

1 <= n <= 2³¹ - 1

Asked at 1 company

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Topics

Hints open one at a time

Hint 1

Simulate as described

3:45

Still stuck?Read the written solution, or watch a walkthrough.

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1class Solution:
2    def getLeastFrequentDigit(self, n: int) -> int:
3        

Starter codePython 3Spaces: 4

Examples

Case 1Case 2

Input

723344511

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