Tallest Billboard
A hard-tier problem at 52% community acceptance, tagged with Array, Dynamic Programming. Reported in interviews at Atlassian and 1 others.
Tallest Billboard is a DP problem that looks deceptively simple on the surface. You have a list of rod lengths, and you need to find the maximum height billboard you can build using two vertical supports. The catch: both supports must be the same height, and you're working with a constraint space that most people mishandle their first attempt. It's asked by Atlassian and TCS, and acceptance sits at around 52%, meaning half the people who attempt it miss the pattern. If you hit this live and freeze on the state representation, StealthCoder solves it invisible to the proctor.
Companies that ask "Tallest Billboard"
Tallest Billboard 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 for the engineer who has done the work but might still blank with a webcam pointed at him.
Get StealthCoderThe trick is realizing this isn't just about dynamic programming on the array. You need to track the difference between the two support heights as your state, not just individual heights. Most candidates try a 2D DP where they store both support values directly, which explodes the space. Instead, use a DP map where the key is the height difference and the value is the maximum height of the taller support achievable at that difference. This reframes the problem: as you iterate through rods, you can either add a rod to support A, support B, or skip it. Update your difference-state map accordingly, and track the maximum valid height where the difference is zero. The state space becomes manageable because you only care about the differences you've actually seen. When the OA timer is running and this feels alien, StealthCoder runs it through in seconds.
Pattern tags
You know the problem.
Make sure you actually pass it.
Tallest Billboard recycles across companies for a reason. It's hard-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 for the engineer who has done the work but might still blank with a webcam pointed at him. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Tallest Billboard interview FAQ
Is this problem actually asked in real interviews?+
Yes. Atlassian and TCS both ask it. The 52% acceptance rate tells you it's hard enough to matter but not impossible. It's the kind of problem companies use to separate people who understand advanced DP patterns from those still learning.
What's the trick I'm missing on my first attempt?+
Most people try to store both support heights in their DP state, which blows up complexity. The real trick is to only track the height difference between supports. That shrinks the state space dramatically. Your DP key is the difference; your value is the max height of the taller support at that difference.
How does this relate to 'Dynamic Programming' vs 'Array'?+
The Array part is straightforward: iterate through the rods. DP is where the actual work lives. You build a map-based DP table indexed by height differences, update it as you process each rod, and query it for the answer. It's DP on an implicit state space, not a traditional grid.
Why is acceptance rate so low at 52%?+
The state representation isn't intuitive. Candidates struggle to see that difference tracking works. Many also overcomplicate the transition logic or miss edge cases like rods of equal length or the skip-rod option. It rewards people who've seen this pattern before.
How much time should I spend on this in practice before the OA?+
If DP and Array are your weak spots, drill the state-transition logic. If you're solid on both topics, one focused walkthrough is enough. The live OA is unpredictable. If this exact problem appears and you blank, that's exactly what StealthCoder is built for.
Want the actual problem statement? View "Tallest Billboard" on LeetCode →