Câu hỏi phỏng vấn Heaps and Maps
Câu hỏi

When would you want to use a Heap?

Câu trả lời

Heaps are a versatile data structure with several practical applications. Here are some scenarios where using a heap is particularly advantageous:

1. Priority Queues

Heaps are commonly used to implement priority queues, where each element has a priority, and elements with higher priorities are processed before those with lower priorities. This is useful in various applications such as:

  • Task scheduling: Managing tasks in an operating system where tasks with higher priority need to be executed first.
  • Event simulation: Handling events in a simulation where events need to be processed in a specific order based on their priority.

2. Sorting Algorithms

Heaps are the foundation of the Heapsort algorithm, which is an efficient comparison-based sorting algorithm with a time complexity of $$O(n \log n)$$. Heapsort is particularly useful when:

  • In-place sorting: You need a sorting algorithm that does not require additional memory beyond the input array.
  • Stable sorting: Although Heapsort is not inherently stable, it can be modified to maintain the relative order of equal elements.

3. Graph Algorithms

Heaps are used in several graph algorithms to efficiently manage and retrieve the next vertex to process. Examples include:

  • Dijkstra’s shortest path algorithm: Using a min-heap to efficiently find the vertex with the smallest tentative distance.
  • Prim’s minimum spanning tree algorithm: Using a min-heap to select the next edge with the smallest weight.

4. Dynamic Median Finding

Heaps can be used to maintain the median of a stream of numbers by using two heaps:

  • Max-heap: To store the smaller half of the numbers.
  • Min-heap: To store the larger half of the numbers.
    This allows efficient retrieval of the median in $$O(\log n)$$ time.

5. Resource Allocation

Heaps can be used to efficiently allocate resources in a system by assigning a priority to each resource and processing requests in order of priority. This is useful in:

  • Memory management: Allocating and deallocating memory blocks dynamically.
  • CPU scheduling: Allocating CPU time to processes based on their priority.

6. Real-Time Applications

Heaps are suitable for real-time applications where elements need to be processed based on priority. Examples include:

  • Load balancing: Distributing tasks across multiple servers based on their current load.
  • Medical applications: Prioritizing patients based on the severity of their condition.

7. Data Compression

Heaps are used in data compression algorithms such as Huffman coding, which uses a priority queue implemented as a ...

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Explain how to find 100 largest numbers out of an array of 1 billion numbers

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