Is Make Array Zero by Subtracting Equal Amounts easy or hard?

The problem is classified as Easy on LeetCode with an acceptance rate around 70%+. The main challenge is recognizing that each distinct positive number corresponds to one operation, which turns the problem into a simple counting task.

Make Array Zero by Subtracting Equal Amounts Python/Java solution

In Python, insert all positive numbers into a set and return its length. In Java, use a HashSet and add each non-zero element while iterating through the array. Both implementations run in O(n) time with O(n) extra space.

How to solve Make Array Zero by Subtracting Equal Amounts in O(n)?

Traverse the array and add every positive element to a hash set. Because each distinct value corresponds to one subtraction operation, the final answer is simply the number of unique non-zero values. This avoids simulating the subtraction process and achieves O(n) time complexity.

What is the best approach for Make Array Zero by Subtracting Equal Amounts?

The best approach is counting the number of distinct non-zero elements in the array. Each unique positive value represents one subtraction round where the smallest remaining value is removed from all positive numbers. Using a hash set allows this to be computed in O(n) time with O(n) space.

Is Make Array Zero by Subtracting Equal Amounts asked at Google/Amazon/Meta?

Problems with similar greedy insights and array processing patterns commonly appear in interviews at companies like Amazon and Google. While this exact problem may not always appear, understanding how to reduce repeated operations into counting distinct values is a useful interview pattern.

What data structure is used in Make Array Zero by Subtracting Equal Amounts?

The optimal solution uses a hash set to track distinct non-zero values in the array. This allows constant-time insertion and ensures each value is counted once. The alternative solution relies on sorting the array and scanning for value transitions.

What is the time complexity of Make Array Zero by Subtracting Equal Amounts?

The optimal solution runs in O(n) time by scanning the array once and inserting non-zero elements into a hash set. The alternative sorting approach runs in O(n log n) time due to the sorting step, followed by a linear scan.

Description Hints 3 Solution Video 6:53

2357. Make Array Zero by Subtracting Equal Amounts

Easy73.8% acceptance1 company

You are given a non-negative integer array nums. In one operation, you must:

Choose a positive integer x such that x is less than or equal to the smallest non-zero element in nums.
Subtract x from every positive element in nums.

Return the minimum number of operations to make every element in nums equal to 0.

Example 1:

Input: nums = [1,5,0,3,5]
Output: 3
Explanation:
In the first operation, choose x = 1. Now, nums = [0,4,0,2,4].
In the second operation, choose x = 2. Now, nums = [0,2,0,0,2].
In the third operation, choose x = 2. Now, nums = [0,0,0,0,0].

Example 2:

Input: nums = [0]
Output: 0
Explanation: Each element in nums is already 0 so no operations are needed.

Constraints:

1 <= nums.length <= 100
0 <= nums[i] <= 100

Asked at 1 company

Amazon

Topics

Hints open one at a time

Hint 1

It is always best to set x as the smallest non-zero element in nums.

Hint 2

Elements with the same value will always take the same number of operations to become 0. Contrarily, elements with different values will always take a different number of operations to become 0.

Hint 3

The answer is the number of unique non-zero numbers in nums.

6:53

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