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Currency Conversion from Exchange Rates
Given a list of direct exchange rates, find the conversion rate between any two currencies, including pairs that have no direct rate.
1. Problem Statement
Given a list of integers, return the maximum sum you can obtain by selecting elements such that no two selected elements are adjacent. You may choose no elements, so return 0 for an empty list or when every value is negative. The list has at most 100000 elements, and each value is between -10000 and 10000 inclusive. Start with any clarifying questions.
2. Live Coding Format
Work in the provided coding workspace while explaining your decisions to the live interviewer. Validation may use inline tests, examples, comments, or a verbal walkthrough.
3. Key Focus Areas
- 1Contract clarification (empty input, all-negative, empty selection allowed)
- 2Approach derivation and correctness argument
- 3Time and space complexity
- 4Edge cases and validation
- 5Follow-up performance
4. What Strong Candidates Should Demonstrate
- Clarify the adjacency constraint, empty selection behaviour, and all-negative edge case.
- Derive a correct approach before coding and argue why it is optimal.
- State the time and auxiliary-space complexity of the final solution.
- Validate with your own examples, including all-negative and single-element inputs, stating expected outputs first.
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Practice this problem in the live coding workspace while the interviewer probes your clarification, implementation, trade-offs, and validation.
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Validate the Binary Search Tree Property
Given the root of a binary tree, determine whether it is a valid binary search tree.
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Cheapest Route Within a Stop Limit
Given one-way routes between cities each with a cost, find the cheapest total cost from a source city to a destination city using at most k intermediate stops.
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Minimum Coins to Reach an Amount
Given a set of coin denominations and a target amount, find the minimum number of coins (with unlimited supply of each denomination) needed to make exactly that amount, or report it is impossible.