Is Transform Array to All Equal Elements easy or hard?

The problem is generally rated Medium because the implementation is simple but the key insight is recognizing the greedy strategy. Many candidates initially try simulation or pairwise operations instead of reducing the task to a frequency counting problem.

Transform Array to All Equal Elements Python/Java solution

The standard implementation uses a dictionary in Python or a HashMap in Java to count element frequencies. After computing the maximum frequency, return n minus that value as the number of required operations. The logic is identical across Python, Java, C++, Go, TypeScript, and Rust.

How to solve Transform Array to All Equal Elements in O(n)?

Traverse the array and count how many times each number appears using a hash map or counter. Track the maximum frequency while iterating. The minimum number of operations needed to make all elements equal is n minus that maximum frequency, since only the non‑matching elements must be changed.

What is the best approach for Transform Array to All Equal Elements?

The optimal approach is a greedy frequency counting strategy. Traverse the array once and compute the frequency of each value using a hash map. The value with the highest frequency should be the final target, and the minimum operations required equals n minus that maximum frequency. This runs in O(n) time with O(n) space.

Is Transform Array to All Equal Elements asked at Google/Amazon/Meta?

Frequency-based greedy array problems appear frequently in interviews at companies like Amazon, Google, and Meta. While the exact problem number may vary across platforms, the pattern of minimizing operations using the most frequent value is a common interview concept.

What data structure is used in Transform Array to All Equal Elements?

A hash map (or dictionary/counter) is typically used to store the frequency of each element in the array. This allows constant-time updates and quick tracking of the most frequent value during a single traversal.

What is the time complexity of Transform Array to All Equal Elements?

The optimal solution runs in O(n) time because the array is traversed once to compute value frequencies. Hash map updates and lookups are O(1) on average. Space complexity is O(n) in the worst case if every element in the array is unique.

Description Hints 2 Solution Video 10:52

3576. Transform Array to All Equal Elements

Medium33.1% acceptance3 companies

You are given an integer array nums of size n containing only 1 and -1, and an integer k.

You can perform the following operation at most k times:

Choose an index i (0 <= i < n - 1), and multiply both nums[i] and nums[i + 1] by -1.

Note that you can choose the same index i more than once in different operations.

Return true if it is possible to make all elements of the array equal after at most k operations, and false otherwise.

Example 1:

Input: nums = [1,-1,1,-1,1], k = 3

Output: true

Explanation:

We can make all elements in the array equal in 2 operations as follows:

Choose index i = 1, and multiply both nums[1] and nums[2] by -1. Now nums = [1,1,-1,-1,1].
Choose index i = 2, and multiply both nums[2] and nums[3] by -1. Now nums = [1,1,1,1,1].

Example 2:

Input: nums = [-1,-1,-1,1,1,1], k = 5

Output: false

Explanation:

It is not possible to make all array elements equal in at most 5 operations.

Constraints:

1 <= n == nums.length <= 10⁵
nums[i] is either -1 or 1.
1 <= k <= n

Asked at 3 companies

Flipkart Microsoft Meta

Topics

Array Greedy

Hints open one at a time

Hint 1

Try converting all elements to 1 and separately to -1. For each case, calculate the minimum number of operations needed.

Hint 2

Use a greedy approach: scan the array from left to right and apply an operation only when needed to fix mismatches.

10:52

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1class Solution:
2    def canMakeEqual(self, nums: List[int], k: int) -> bool:
3        

Starter codePython 3Spaces: 4

Examples

Case 1Case 2

Input

[1,-1,1,-1,1]
3

Input

[-1,-1,-1,1,1,1]
5

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