SEARCH SORTED LIST<LONG> FOR CLOSEST AND LESS THAN

Lady Bird Johnson

Total Post:20

Points:140
Posted by  Lady Bird Johnson
C# 
C#
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Consider some long called X and a sorted List<Long>. What is the most efficient algorithm to find the index or value in the List<Long> that is (i) less than X, and (ii) The closest to X on the number line (assuming condition (i) has been satsified)?

For example this could be a problem setup:

long X = 500;
List<Long> foo = new Arraylist<Long>();
foo.add(450L);
foo.add(451L);    
foo.add(499L);
foo.add(501L);
foo.add(550L);
 
Collections.sort(foo); // It's always sorted.

I would like the algorithm to either return 499 or to return the index associated with 499 (in this casei=2).

  1. Hank Greenberg

    Post:12

    Points:84
    Re: Search sorted List<Long> for closest and less than

    If 499 is unique than, use indexOf(Object) method.

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