I doubt there is a general purpose binary search method in .NET like that, except for the one being present in some base classes (but apparently not in the interfaces), so here’s my general purpose one. public static Int32 BinarySearchIndexOf<T>(this IList<T> list, T value, IComparer<T> comparer = null) { if (list == null) throw new … Read more
In a sorted container, the last element that is less than or equivalent to x, is the element before the first element that is greater than x. Thus you can call std::upper_bound, and decrement the returned iterator once. (Before decrementing, you must of course check that it is not the begin iterator; if it is, … Read more
A linear search looks down a list, one item at a time, without jumping. In complexity terms this is an O(n) search – the time taken to search the list gets bigger at the same rate as the list does. A binary search is when you start with the middle of a sorted list, and … Read more
Those functions are located in the bisect module: bisect.bisect_left(a, x, lo=0, hi=len(a)) is the analog of std::lower_bound(). bisect.bisect_right(a, x, lo=0, hi=len(a)) is the analog of std::upper_bound(). Note: there is also a function bisect() which is an alias for bisect_right().
When index is unique, pandas use a hashtable to map key to value O(1). When index is non-unique and sorted, pandas use binary search O(logN), when index is random ordered pandas need to check all the keys in the index O(N). You can call sort_index method: import numpy as np import pandas as pd x … Read more
This question was just asked again recently. Apart from Knuth’s quote that “Although the basic idea of binary search is comparatively straightforward, the details can be surprisingly tricky”, there is the staggering historical fact (see TAOCP, Volume 3, section 6.2.1) that binary search was first published in 1946 but the first published binary search without … Read more
One way of thinking about this problem is to think about doing a binary search over a transformed version of the array, where the array has been modified by applying the function f(x) = 1 if x > target 0 else Now, the goal is to find the very first place that this function takes … Read more
It’s useful to write a search function in such a way that it returns a negative value indicating the insertion point for the new element if the element is not found. Also, using recursion in a binary search is excessive and unnecessary. And finally, it’s a good practice to make the search algorithm generic by … Read more
For very small collections the difference is going to be negligible. At the low end of your range (500k items) you will start to see a difference if you’re doing lots of lookups. A binary search is going to be O(log n), whereas a hash lookup will be O(1), amortized. That’s not the same as … Read more
This post covers this famous bug in a lot of detail. As others have said it’s an overflow issue. The fix recommended on the link is as follows: int mid = low + ((high – low) / 2); // Alternatively int mid = (low + high) >>> 1; It is also probably worth mentioning that … Read more