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71 lines
2.5 KiB
JavaScript
71 lines
2.5 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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export var BinarySearch = Object.freeze({
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/**
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* Returns the index of the given target in the given array or -1 if the
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* target is not found.
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*
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* See search() for a description of this function's parameters.
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*
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* @return The index of `target` in `array` or -1 if `target` is not found.
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*/
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indexOf(comparator, array, target) {
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let [found, idx] = this.search(comparator, array, target);
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return found ? idx : -1;
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},
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/**
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* Returns the index within the given array where the given target may be
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* inserted to keep the array ordered.
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*
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* See search() for a description of this function's parameters.
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*
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* @return The index in `array` where `target` may be inserted to keep `array`
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* ordered.
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*/
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insertionIndexOf(comparator, array, target) {
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return this.search(comparator, array, target)[1];
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},
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/**
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* Searches for the given target in the given array.
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*
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* @param comparator
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* A function that takes two arguments and compares them, returning a
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* negative number if the first should be ordered before the second,
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* zero if the first and second have the same ordering, or a positive
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* number if the second should be ordered before the first. The first
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* argument is always `target`, and the second argument is a value
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* from the array.
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* @param array
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* An array whose elements are ordered by `comparator`.
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* @param target
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* The value to search for.
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* @return An array with two elements. If `target` is found, the first
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* element is true, and the second element is its index in the array.
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* If `target` is not found, the first element is false, and the
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* second element is the index where it may be inserted to keep the
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* array ordered.
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*/
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search(comparator, array, target) {
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let low = 0;
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let high = array.length - 1;
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while (low <= high) {
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// Thanks to http://jsperf.com/code-review-1480 for this tip.
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let mid = (low + high) >> 1;
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let cmp = comparator(target, array[mid]);
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if (cmp == 0) {
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return [true, mid];
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}
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if (cmp < 0) {
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high = mid - 1;
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} else {
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low = mid + 1;
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}
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}
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return [false, low];
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},
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});
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