Minimum Cost to Convert String II
A hard-tier problem at 26% community acceptance, tagged with Array, String, Dynamic Programming. Reported in interviews at Atlassian and 0 others.
Minimum Cost to Convert String II is a hard problem that's started showing up in Atlassian's assessment rounds. With a 25% acceptance rate, you're looking at a problem that trips up most candidates who see it cold. The challenge: you need to transform one string into another using allowed conversions, each with a cost, and find the minimum total cost. It's not a straight DP problem, and the greedy instinct usually leads you into a wall. If you hit this during the OA and the pattern isn't obvious, StealthCoder surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "Minimum Cost to Convert String II"
Minimum Cost to Convert String II 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. Built by an engineer at a top-10 tech company who can solve these problems cold but didn't want to trust himself in a 90-minute screen share.
Get StealthCoderThe trap here is thinking you can greedily apply the cheapest conversion at each step. You can't. The real solution combines graph shortest-path logic with dynamic programming and often a Trie to handle multiple overlapping conversion patterns efficiently. You're essentially building a graph where nodes are character states and edges are conversions with costs, then querying shortest paths. The DP layer handles string matching character by character or substring by substring, depending on the problem variant. Most candidates either oversimplify to greedy or get lost in the implementation complexity. StealthCoder is your safety net if the Trie and shortest-path combo doesn't click during the live assessment.
Pattern tags
You know the problem.
Make sure you actually pass it.
Minimum Cost to Convert String II 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. Built by an engineer at a top-10 tech company who can solve these problems cold but didn't want to trust himself in a 90-minute screen share. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Minimum Cost to Convert String II interview FAQ
Is this really harder than standard DP string problems?+
Yes. It combines DP, Trie construction, and graph shortest-path in one pass. Standard DP string problems don't require the shortest-path layer. The 25% acceptance rate reflects that the problem tests multiple algorithmic domains simultaneously.
Why doesn't a greedy approach work?+
Because a cheaper immediate conversion might block a much cheaper multi-step path later. Conversions can overlap or chain in ways that make the order of application matter. You need to explore all valid paths and pick the minimum, not just the locally cheapest option.
Do I need to build a Trie?+
Likely yes, especially if conversions are variable-length substrings. A Trie helps you quickly find all valid conversions starting at each position without redundant string comparisons. It's not mandatory but makes the DP layer much faster.
How does this relate to the Graph and Shortest Path topics?+
The conversions define a weighted directed graph where each node is a character or state and edges are conversion rules with costs. Finding minimum conversion cost is a shortest-path problem, often solved with Dijkstra or Bellman-Ford depending on the constraint.
Is this still asked, or is it a one-off at Atlassian?+
It's confirmed asked at Atlassian. With only one top company on record and hard difficulty, it's not a mainstream problem yet. That means less public discussion and fewer prepared candidates. If it appears in your OA, it's likely a differentiator round.
Want the actual problem statement? View "Minimum Cost to Convert String II" on LeetCode →