To solve Calculate Score After Performing Instructions, process the instructions sequentially, updating a running score based on add or jump actions. Use a hash table to track values efficiently for fast lookup and prevent redundant computations. This approach ensures correct simulation while keeping time complexity manageable, especially for large arrays with up to 10^5 elements.
Problem Statement
You are given two arrays of length n: instructions and values. Each instruction is either 'add' or 'jump', and values contains corresponding integer numbers. You must simulate the instructions starting from index 0, modifying a running score according to the rules below.
Follow these rules step by step: for an 'add' instruction, add the value to your score; for a 'jump' instruction, move the pointer by the value. The process ends when the pointer moves outside the array bounds or all instructions are processed. Return the final score after simulating all instructions.
Examples
Example 1
Input: instructions = ["jump","add","add","jump","add","jump"], values = [2,1,3,1,-2,-3]
Output: 1
Simulate the process starting at instruction 0:
Example 2
Input: instructions = ["jump","add","add"], values = [3,1,1]
Output: 0
Simulate the process starting at instruction 0:
Example 3
Input: instructions = ["jump"], values = [0]
Output: 0
Simulate the process starting at instruction 0:
Constraints
- n == instructions.length == values.length
- 1 <= n <= 105
- instructions[i] is either "add" or "jump".
- -105 <= values[i] <= 105
Solution Approach
Sequential Simulation
Iterate through the instructions array, applying each 'add' or 'jump' in order. Keep track of the current index and update the running score on 'add'. For 'jump', adjust the index and verify bounds to prevent errors. This directly follows the array scanning plus hash lookup pattern.
Hash Table Optimization
Use a hash table to record previous positions or values to avoid repeated computation on identical sequences. This ensures that when similar instructions or values occur, you can retrieve prior results instantly, maintaining efficiency for large n.
Edge Case Handling
Carefully handle negative jumps and boundary conditions. Ensure that adding negative values or jumping beyond array limits does not cause runtime errors. Always check the hash table first for existing entries to prevent unnecessary recalculation.
Complexity Analysis
| Metric | Value |
|---|---|
| Time | Depends on the final approach |
| Space | Depends on the final approach |
Time complexity is O(n) for scanning all instructions with O(1) hash lookups per operation. Space complexity is O(n) due to storing positions or values in the hash table for fast access.
What Interviewers Usually Probe
- Focus on array scanning combined with hash table lookups.
- Check edge conditions for jumps going out of array bounds.
- Look for opportunities to reuse computed values for repeated sequences.
Common Pitfalls or Variants
Common pitfalls
- Failing to check array bounds after a jump, leading to runtime errors.
- Overwriting or ignoring previous hash entries, causing incorrect scores.
- Confusing the order of add and jump operations when updating score.
Follow-up variants
- Instructions could include multiply operations requiring dynamic score adjustments.
- Allow variable-length jumps based on previous scores, increasing simulation complexity.
- Use nested instruction sequences, requiring multi-level hash tracking for correctness.
How GhostInterview Helps
- Provides step-by-step guidance simulating add and jump instructions for correct score computation.
- Highlights hash table usage to prevent redundant calculations on repeated instruction patterns.
- Explains edge case handling for negative jumps and array boundaries efficiently.
Topic Pages
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- Coding Interview Assistant - See how GhostInterview supports array, string, linked list, graph, and tree interview workflows.
- How GhostInterview Works - Review the screenshot, reasoning, and answer flow before using the solver in a live interview.
FAQ
What is the main strategy for Calculate Score After Performing Instructions?
Simulate instructions sequentially while tracking values with a hash table to efficiently compute the final score.
Can jumps move the pointer outside the array?
Yes, the process ends immediately if a jump causes the pointer to go out of bounds.
How do I handle repeated instruction sequences?
Use a hash table to store previously computed results for identical sequences to avoid recalculation.
Are negative values allowed in the instructions array?
Yes, negative values can occur and must be handled correctly for both add and jump operations.
Why is array scanning plus hash lookup crucial here?
Because it allows fast traversal of instructions while quickly accessing prior results to maintain efficiency on large inputs.
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