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Add jump search algo #157

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Merged
merged 2 commits into from
Apr 7, 2020
Merged

Add jump search algo #157

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2ea7983
Add jump search algo
duffman85 Oct 26, 2019
e3ae54a
Update src/searching/jump-search.js
mgechev Apr 7, 2020
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56 changes: 56 additions & 0 deletions src/searching/jump-search.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,56 @@
(function(exports) {
'use strict';
/**
* Searches for specific element in a given array using
* the jump search algorithm.<br><br>
* Time complexity: O(log N).
*
* @example
*
* var search = require('path-to-algorithms/src/searching/'+
* 'jump-search').jumpSearch;
* console.log(search([1, 2, 3, 4, 5], 4)); // 3
*
* @public
* @module searching/jumpsearch
* @param {Array} sortedArray Input array.
* @param {Number} seekIndex of the element which index should be found.
* @returns {Number} Index of the element or -1 if not found.
*/
function jumpSearch(sortedArray, seekIndex) {
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The Index suffix here is a bit misleading.

// exit if array empty
const arrayLength = sortedArray.length;
if (!arrayLength) {
return -1;
}

// set jumpSize
const jumpSize = Math.floor(Math.sqrt(arrayLength));

let blockStart = 0;
let blockEnd = jumpSize;

while (seekIndex > sortedArray[Math.min(blockEnd, arrayLength) - 1]) {
blockStart = blockEnd;
blockEnd += jumpSize;

// if out of array bounds exit
if (blockStart > arrayLength) {
return -1;
}
}

let currentIndex = blockStart;
while (currentIndex < Math.min(blockEnd, arrayLength)) {
if (sortedArray[currentIndex] === seekIndex) {
return currentIndex;
}

currentIndex += 1;
}

return -1;
}

exports.jumpSearch = jumpSearch;
})(typeof window === 'undefined' ? module.exports : window);
21 changes: 21 additions & 0 deletions test/searching/jump-search.spec.js
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Original file line number Diff line number Diff line change
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var jumpSearch = require('../../src/searching/jump-search').jumpSearch;

describe('Jump search', function() {
'use strict';

it('should find the element at position 0 ', function() {
expect(jumpSearch([1, 2, 3, 4, 6, 8], 1)).toBe(0);
});

it('should find the element at position 4 ', function() {
expect(jumpSearch([1, 2, 3, 4, 6, 8], 6)).toBe(4);
});

it('should return -1 ', function() {
expect(jumpSearch([1, 2, 3, 4, 6, 8], 10)).toBe(-1);
});

it('should return -1 ', function() {
expect(jumpSearch([], 10)).toBe(-1);
});
});