Find the largest 100 numbers from 1 billion integers
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Suppose you are given 1 billion \( (1\times 10^{9}) \) unsorted integers on one disk file. How would you determine the largest 100 numbers?


Posted Answers

The algorithm works as :


  • Create a min heap with the first 100 numbers.
  • From the remaining unsorted array take each element at a time, insert it into the min heap into its correct position (heapify) and delete the root (minimum value) from the min heap.
  • Repeat the last step until the end of the remaining unsorted integers.
  • Now the heap contains the largest 100 numbers.


Time complexity = \( O(nlogm) \).
where n = Total number of integers in the unsorted array;
m = heap size (Here m=100 ).

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