Make Array Zero by Subtracting Equal Amounts

Published: Sep 21, 2022

Introduction

This problem looks like a simulation required. However, if we carefully read the problem, it turns out the answer is just a number of times. Think what will go on from the problem description. The number of unique non-zero values is the answer.

Problem Description

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.

Constraints:

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

https://leetcode.com/problems/make-array-zero-by-subtracting-equal-amounts/

Examples

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.

Analysis

The answer is the number of unique non-zero values, so take a set at first. If 0 doesn’t exist in the set, the length of the set is the answer. Otherwise subtract 1 from the length of the set.

Solution

class MakeArrayZeroBySubtractingEqualAmounts:
    def minimumOperations(self, nums: List[int]) -> int:
        ss = set(nums)
        return len(ss) if 0 not in ss else len(ss) - 1

Complexities

• Time: O(n)
• Space: O(n)