Make Array Zero by Subtracting Equal Amounts

Published: Sep 21, 2022

Easy Simulation Array Hash Table


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.


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


Example 1
Input: nums = [1,5,0,3,5]
Output: 3
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.


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.


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


  • Time: O(n)
  • Space: O(n)