Merge 7e454924de into ca3d16dcce

src/algorithms/search/sentinal-linear-search/README.md

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+# Sentinal Linear Search
+The idea in Sentinal Linear Search is to reduce the number of comparisons required to find an element in a list. Here we replace the last element of the list with the search element itself and run a while loop to see if there exists any copy of the search element in the list and quit the loop as soon as we find the search element.
+
+## Complexity
+
+**Time Complexity**: `O(n)` - since we're checking each element in the array
+
+##Reference
+- [Wikipedia] (https://en.wikipedia.org/wiki/Linear_search)

src/algorithms/search/sentinal-linear-search/__test__/sentinalLinearSearch.test.js

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+import sentinalLinearSearch from '../sentinalLinearSearch';
+
+describe('sentinalLinearSearch', () => {
+  it('should search all numbers in array', () => {
+    const array = [1, 2, 4, 6, 2, 1, 5, 2];
+
+    expect(sentinalLinearSearch(array, 10)).toEqual([]);
+    expect(sentinalLinearSearch(array, 1)).toEqual([0, 5]);
+    expect(sentinalLinearSearch(array, 2)).toEqual([1, 4, 7]);
+  });
+
+  it('should search all strings in array', () => {
+    const array = ['a', 'b', 'a', 'c', 'd', 'a', 'r'];
+
+    expect(sentinalLinearSearch(array, 'c')).toEqual([3]);
+    expect(sentinalLinearSearch(array, 'b')).toEqual([1]);
+    expect(sentinalLinearSearch(array, 'a')).toEqual([0, 2, 5]);
+  });
+});

src/algorithms/search/sentinal-linear-search/sentinalLinearSearch.js

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+import Comparator from '../../../utils/comparator/Comparator';
+
+/**
+ * Sentinal Linear search implementation.
+ *
+ * @param {*[]} array
+ * @param {*} seekElement
+ * @param {function(a, b)} [comparatorCallback]
+ * @return {number[]}
+ */
+export default function sentinalLinearSearch(array, seekElement, comparatorCallback) {
+  const comparator = new Comparator(comparatorCallback);
+  const foundIndices = [];
+  const lastEle = array[array.length - 1]; // Picking the last element in the array
+  const i = 0;
+
+  while (comparator.notEqual(i, array.length - 1)) {
+    while(comparator.notEqual(array[i], seekElement)) {
+      i = i + 1;
+    }
+    if(comparator.notEqual(i, array.length - 1)) {
+      foundIndices.push(i);
+      i = i + 1;
+    }
+  }
+  array[array.length - 1] = lastEle; // Replacing the last element
+
+  if (comparator.equal(array[array.length - 1], seekElement)) {
+    foundIndices.push(i);
+  }
+  return foundIndices;
+}