Merge Operations to Turn Array Into a Palindrome
A medium-tier problem at 69% community acceptance, tagged with Array, Two Pointers, Greedy. Reported in interviews at Accolite and 0 others.
You've got an array and you need to turn it into a palindrome by merging adjacent elements. Accolite has asked this one. The twist is that merging elements combines their values, and you want the minimum number of operations to make the array read the same forwards and backwards. Most candidates overthink the merge order. You either spot the greedy pattern immediately or you're stuck trying every combination. If this hits your live OA and you blank on the strategy, StealthCoder solves it in seconds, invisible to the proctor.
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Merge Operations to Turn Array Into a Palindrome is the kind of problem that decides whether you pass. StealthCoder reads the problem on screen and surfaces a working solution in under 2 seconds. Invisible to screen share. The proctor sees nothing. Made by an Amazon engineer who watched the leaked-problem repo become an industry secret. He decided you should have it too.
Get StealthCoderThe core insight is two-pointers from opposite ends. Start with the leftmost and rightmost elements. If they're equal, move inward. If they're not, you must merge one of them with its neighbor. The greedy choice is to merge the smaller value, since a smaller sum is easier to match on the opposite side later. Keep merging and comparing until pointers meet. The trap is trying to precompute which merges to do or backtracking when a merge fails. The actual solution is linear once you realize merging is forced, and greedy selection works because you're always making the locally optimal choice that doesn't block future matches. This is where StealthCoder shines on live OAs: the algorithm is short but the implementation detail of tracking merged values catches people off guard under time pressure.
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Merge Operations to Turn Array Into a Palindrome recycles across companies for a reason. It's medium-tier, and most candidates blank under the timer. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds. Made by an Amazon engineer who watched the leaked-problem repo become an industry secret. He decided you should have it too. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Merge Operations to Turn Array Into a Palindrome interview FAQ
Is this problem actually about finding the minimum merge operations?+
Yes. Count the number of adjacent-element merges needed to make the array a palindrome. Each merge combines two values into one, reducing array length. The goal is the minimum operation count to achieve palindrome state.
Do I have to try all possible merge sequences?+
No. The two-pointer greedy approach is linear and optimal. Merge the smaller of the two mismatched outer elements toward the larger, then compare again. Backtracking or DP is overkill and signals you missed the greedy pattern.
What happens when you merge two elements?+
Their values sum into a single element. That new sum now compares to the opposite side. If the opposite side is larger, you merge again. Greedy always merges the smaller value to avoid cascading forced merges on the other side.
Is this problem still asked after the medium-difficulty update?+
It's rare but it has been reported at Accolite. Acceptance rate is around 69 percent, so most people who attempt it pass. The gap is in recognizing the two-pointer greedy pattern on first read.
How does this relate to Two Pointers and Greedy algorithms?+
Two Pointers scan the array from both ends simultaneously. Greedy means you always merge the smaller mismatched element without looking ahead. Together they form the complete solution: iterate inward with greedy merge choices.
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