binary-search-bounds

Better binary searching

npm install binary-search-bounds
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binary-search-bounds

Binary search on arrays. Also works if the inputs are 1D ndarrays.

API

var bounds = require("binary-search-bounds")

bounds.lt(array, y[, cmp, lo, hi])

Returns the index of the last item in the array < y

bounds.le(array, y[, cmp, lo, hi])

Returns the index of the last item in the array <= y

bounds.gt(array, y[, cmp, lo, hi])

Returns the index of the first item in the array > y

bounds.ge(array, y[, cmp, lo, hi])

Returns the index of the first item in the array >= y

bounds.eq(array, y[, cmp, lo, hi])

Returns an index of some item in the array == y. -1 if not found.

Notes

  • array can be either an array or an ndarray
  • cmp is a comparison function, just like what you would pass to Array.sort()
  • y will always be the second argument passed to cmp, so you can ignore it if you are just binary searching on a predicate
  • Assumes the array is sorted as would be the case if you called Array.sort(cmp) on it
  • If no comparison is passed, assume array is sorted in ascending order (note this is different than the semantics of Array.sort() which converts all entries to strings if you don't pass an argument)
  • lo gives a lower bound on the array index to search
  • hi gives an upper bound on the array index to search
  • bounds.le and bounds.lt will return lo - 1 if no element is found satisfying the predicate
  • bounds.ge and bounds.gt will return hi + 1 if no element is found satisfying the predicate
  • bounds.eq will return the first found item with the given index. It can be a little faster than the other methods if you just want to find some random match.

Credits

(c) 2013 Mikola Lysenko. MIT License

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