Min Operations to Make All Elements Equal
Reported by candidates from IBM's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
IBM asked this in September 2024, and it's a pattern you need to recognize fast. You're given an array and need to find the minimum operations to make every element the same value. The trap is thinking you need to pick the target value dynamically. Most candidates burn time on greedy guesses or brute force. StealthCoder reads the problem, spots the math trick, and feeds you the formula when you blank. The real insight is understanding what 'operations' means and which target minimizes them.
Pattern and pitfall
The core move here is recognizing that the optimal target is almost always the median or mean of the array, depending on what counts as an operation. If each operation changes one element by 1, you're minimizing the sum of absolute differences, which is a classic median problem. If operations are more complex (changing multiple elements at once, or doubling/halving), you need to recalibrate. The pattern is math plus greedy: calculate the cost to reach each candidate target, pick the cheapest. Don't overthink which target works; test the median and the arithmetic mean. StealthCoder handles the formula lookup when the operation rules get weird. Most candidates lose points here because they implement a correct algorithm but pick the wrong target.
Drill it cold or hedge it with StealthCoder. Either way, don't walk into the OA hoping you remember the trick.
You can drill Min Operations to Make All Elements Equal cold, or you can hedge it. StealthCoder runs invisibly during screen share and surfaces a working solution in under 2 seconds. The proctor sees the IDE. They don't see what's behind it. Made for the candidate who got the OA invite this morning and has 72 hours, not six months.
Get StealthCoderRelated leaked OAs
This OA pattern shows up on LeetCode as minimum cost to make array equal. If you have time before the OA, drill that.
You've seen the question.
Make sure you actually pass IBM's OA.
IBM reuses patterns across OAs. Made for the candidate who got the OA invite this morning and has 72 hours, not six months. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Min Operations to Make All Elements Equal FAQ
What's the actual operation in the problem?+
That's critical. If it's 'change one element by 1,' the answer is the sum of distances to the median. If it's something else (multiply, add a constant, swap), the formula changes completely. Read the problem statement twice. The operation definition lives there.
Is the target value always in the array?+
Not always. Usually the optimal target is the median (for sum of distances) or somewhere between the min and max. Test a range if the problem doesn't restrict it. If the target must be an array element, brute force all n values; it's O(n squared) but small arrays make it fast enough.
How do I pick the target in 2 minutes?+
Calculate cost to reach the median first. That's your baseline. Then quickly check the floor and ceiling of the mean. Pick whichever costs least. If the array is small, brute force all unique values. Speed over perfection here.
Is this a dynamic programming problem?+
Rarely. DP shows up if operations have ordering constraints or you're building up the array incrementally. Most versions are pure math. If you're tempted to use memoization, you've probably overcomplicited it. Step back and think about the target value.
What if the array is huge and I can't brute force?+
Sort the array once. The median is the middle element (or average of two middles if even length). Use that as your target, calculate total cost in O(n). Done. Sorting is your secret weapon for large inputs. Avoid iterating over every possible target value.