Add Ternary search

src/_Searching_/TernarySearch/TernarySearch.test.js

@@ -0,0 +1,41 @@
+const { ternarySearch, ternarySearchRecursive } = require('.');
+
+describe('Ternary Search', () => {
+  const array = [1, 2, 3, 4, 5, 6, 7, 8];
+  const low = 0;
+  const high = array.length - 1;
+
+  describe('When element to find is at 1st position ', () => {
+    it('Ternary search with Loop', () => {
+      expect(ternarySearch(array, 1)).toEqual(0);
+    });
+    it('Ternary serach with recursion', () => {
+      expect(ternarySearchRecursive(array, low, high, 1)).toEqual(0);
+    });
+  });
+  describe('When element to find is at last position ', () => {
+    it('Ternary search with Loop', () => {
+      expect(ternarySearch(array, 7)).toEqual(6);
+    });
+    it('Ternary serach with recursion', () => {
+      expect(ternarySearchRecursive(array, low, high, 7)).toEqual(6);
+    });
+  });
+  describe('When element to find is at random position ', () => {
+    it('Ternary search with Loop', () => {
+      expect(ternarySearch(array, 3)).toEqual(2);
+    });
+    it('Ternary serach with recursion', () => {
+      expect(ternarySearchRecursive(array, low, high, 3)).toEqual(2);
+    });
+  });
+  describe('When element to find is no present in array ', () => {
+    it('Ternary search with Loop', () => {
+      expect(ternarySearch(array, 10)).toEqual(null);
+    });
+    it('Ternary serach with recursion', () => {
+      expect(ternarySearchRecursive(array, low, high, 10)).toEqual(null);
+    });
+  });
+
+});

src/_Searching_/TernarySearch/index.js

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+/**
+ * Note: Array must be sorted for binary search
+ * Complexity: 
+ * Worst case time complexity: O(log N)
+ * Average case time complexity: O(log N)
+ * Best case time complexity: O(1)
+ * Space complexity: O(1)
+*/
+function ternarySearch(arr, key){
+    let left = 0;
+    let right = arr.length - 1;
+    while(left <= right){
+        let temp2 = left + Math.floor((right - left) / 3);
+        let temp3 = left + 2 * Math.floor((right - left) / 3);
+        if(key == arr[left]){
+            return left;
+        } else if(key  == arr[right]){
+            return right;
+        } else if(key < arr[left] || key > arr[right]){
+            return null;
+        } else if(key <= arr[temp2]){
+            right = temp2;
+        } else if(key > arr[temp2] && key <= arr[temp3]){
+            left = temp2 + 1;
+            right = temp3;
+        } else {
+            left = temp3 + 1;
+        }
+    }
+    return null;
+}
+
+function ternarySearchRecursive(arr, low, high, key){
+
+    if(high >= low){
+        let highMiddle = low + 2 * Math.floor((high - low) / 3);
+        let lowMiddle = low + Math.floor((high - low) / 3);
+        if(key === arr[lowMiddle]){
+            return lowMiddle;
+        } else if(key === arr[highMiddle]){
+            return highMiddle;
+        } else if(key < arr[highMiddle]){
+            return ternarySearchRecursive(arr, low, lowMiddle, key);
+        } else if(key > arr[lowMiddle] && key < arr[highMiddle]){
+            return ternarySearchRecursive(arr, lowMiddle, highMiddle, key);
+        } else if(arr.indexOf(key) == - 1){
+            return null;
+        } else {
+            return ternarySearchRecursive(arr, highMiddle, high, key);
+        } 
+    } 
+    return null;
+}
+
+module.exports = {
+    ternarySearch,
+    ternarySearchRecursive
+};