47 lines
1.3 KiB
JavaScript
47 lines
1.3 KiB
JavaScript
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(function (exports) {
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'use strict';
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function id (val) { return val; }
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function get (key) { return function (val) { return val[key]; }; }
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/**
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* Searches for specific element in a given array using
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* the binary search algorithm.<br><br>
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* Time complexity: O(log N).
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*
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* @example
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*
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* var search = require('path-to-algorithms/src/searching/'+
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* 'binarysearch').binarySearch;
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* console.log(search([1, 2, 3, 4, 5], 4)); // 3
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*
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* @public
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* @module searching/binarysearch
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* @param {Array} array Input array.
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* @param {Number} value Value of the element which index should be found.
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* @returns {Number} Index of the element or -1 if not found.
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*/
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function binarySearch(array, value, key) {
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key = !key ? id : typeof key === 'string' ? get(key) : key;
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value = key(value);
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var middle = Math.floor(array.length / 2);
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var left = 0;
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var right = array.length;
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while (right >= left) {
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var middleValue = key(array[middle]);
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if (middleValue === value) {
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return middle;
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} else if (middleValue > value) {
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right = middle - 1;
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} else {
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left = middle + 1;
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}
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middle = Math.floor((left + right) / 2);
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}
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return -1;
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}
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exports.binarySearch = binarySearch;
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})(typeof window === 'undefined' ? module.exports : window);
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