Add jump search algo (mgechev#157)

* Add jump search algo

* Update src/searching/jump-search.js

Co-authored-by: Minko Gechev <[email protected]>

Author: duffman85

src/searching/jump-search.js

@@ -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) {
+    // 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);

test/searching/jump-search.spec.js

@@ -0,0 +1,21 @@
+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);
+  });
+});