mirror of
https://github.com/TheAlgorithms/JavaScript.git
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c6a36987c8
* BinarySearchIterative Function is added * BinarySearch function is renamed to BinarySearchRecurisve * changes in test function - 3 binarySearchRecursive tests - 3 binarySearchIterative tests
94 lines
2.4 KiB
JavaScript
94 lines
2.4 KiB
JavaScript
/* Binary Search: https://en.wikipedia.org/wiki/Binary_search_algorithm
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*
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* Search a sorted array by repeatedly dividing the search interval
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* in half. Begin with an interval covering the whole array. If the value of the
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* search key is less than the item in the middle of the interval, narrow the interval
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* to the lower half. Otherwise narrow it to the upper half. Repeatedly check until the
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* value is found or the interval is empty.
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*/
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function binarySearchRecursive (arr, x, low = 0, high = arr.length - 1) {
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const mid = Math.floor(low + (high - low) / 2)
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if (high >= low) {
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if (arr[mid] === x) {
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// item found => return its index
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return mid
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}
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if (x < arr[mid]) {
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// arr[mid] is an upper bound for x, so if x is in arr => low <= x < mid
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return binarySearchRecursive(arr, x, low, mid - 1)
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} else {
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// arr[mid] is a lower bound for x, so if x is in arr => mid < x <= high
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return binarySearchRecursive(arr, x, mid + 1, high)
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}
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} else {
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// if low > high => we have searched the whole array without finding the item
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return -1
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}
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}
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function binarySearchIterative (arr, x, low = 0, high = arr.length - 1) {
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while (high >= low) {
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const mid = Math.floor(low + (high - low) / 2)
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if (arr[mid] === x) {
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// item found => return its index
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return mid
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}
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if (x < arr[mid]) {
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// arr[mid] is an upper bound for x, so if x is in arr => low <= x < mid
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high = mid - 1
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} else {
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// arr[mid] is a lower bound for x, so if x is in arr => mid < x <= high
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low = mid + 1
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}
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}
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// if low > high => we have searched the whole array without finding the item
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return -1
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}
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/* ---------------------------------- Test ---------------------------------- */
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const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
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const stringArr = [
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'Alpha',
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'Bravo',
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'Charlie',
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'Delta',
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'Echo',
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'Foxtrot',
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'Golf',
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'Hotel',
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'India',
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'Juliet',
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'Kilo',
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'Lima',
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'Mike',
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'November',
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'Oscar',
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'Papa',
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'Quebec',
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'Romeo',
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'Sierra',
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'Tango',
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'Uniform',
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'Victor',
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'Whiskey',
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'X-Ray',
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'Yankee',
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'Zulu'
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]
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console.log(binarySearchRecursive(arr, 3))
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console.log(binarySearchIterative(arr, 7))
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console.log(binarySearchRecursive(arr, 13))
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console.log(binarySearchIterative(stringArr, 'Charlie'))
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console.log(binarySearchRecursive(stringArr, 'Zulu'))
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console.log(binarySearchIterative(stringArr, 'Sierra'))
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