Add day 29

README.md

@@ -52,6 +52,7 @@ Read [CONTRIBUTING.md](./CONTRIBUTING.md) for contribution guidelines.
 26. [Day 26 -- Spiral Generation and Copy](./day26) -- [http://codetoexpress.tech/dc/day26/](http://codetoexpress.tech/dc/day26/)
 27. [Day 27 -- The Minesweeper Problem](./day27) -- [http://codetoexpress.tech/dc/day27/](http://codetoexpress.tech/dc/day27/)
 28. [Day 28 -- Linear Search](./day28) -- [http://codetoexpress.tech/dc/day28/](http://codetoexpress.tech/dc/day28/)
+29. [Day 29 -- Linear Search](./day29) -- [http://codetoexpress.tech/dc/day29/](http://codetoexpress.tech/dc/day29/)
 
 ## [More Problems](./BONUS/README.md)
 

day29/JavaScript/binary.js

@@ -0,0 +1,20 @@
+function binarySearch(arr, elem) {
+    var start = 0;
+    var end = arr.length - 1;
+    var middle = Math.floor((start + end) / 2);
+    while(arr[middle] !== elem && start <= end) {
+        if(elem < arr[middle]){
+            end = middle - 1;
+        } else {
+            start = middle + 1;
+        }
+        middle = Math.floor((start + end) / 2);
+    }
+    if(arr[middle] === elem){
+        return middle;
+    }
+    return undefined;
+}
+
+console.log (binarySearch ([1, 2, 3, 4, 5, 8, 9], 8)); // 5
+console.log (binarySearch ([1, 2, 3, 4, 5, 8, 9], 7)); // undefined

day29/README.md

@@ -0,0 +1,50 @@
+![cover](./cover.png)
+
+# Day 28 - Search and Sort Algorithms Part B: The Binary Search
+
+Binary Search is searching technique which works on Divide and Conquer approach. Indeed an efficient searching algorithm with a runtime of `O(log(n))`, but it works only on sorted arrays.
+
+## Question
+
+Given a sorted array, and a number n, write a program to implement binary search and finid the index of the given number.
+
+Try to do it using recursion as well as iteration.
+
+**Example**
+
+```
+input: arr = [1, 2, 3, 4, 5, 8, 9], num = 8
+output: 5 (index of found element)
+
+input: arr = [1, 2, 3, 4, 5, 8, 9], num = 7
+output: undefined
+```
+
+![ques](./ques.png)
+
+## Solution
+
+### [JavaScript Implementation](./JavaScript/binary.js)
+
+```js
+function binarySearch(arr, elem) {
+    var start = 0;
+    var end = arr.length - 1;
+    var middle = Math.floor((start + end) / 2);
+    while(arr[middle] !== elem && start <= end) {
+        if(elem < arr[middle]){
+            end = middle - 1;
+        } else {
+            start = middle + 1;
+        }
+        middle = Math.floor((start + end) / 2);
+    }
+    if(arr[middle] === elem){
+        return middle;
+    }
+    return undefined;
+}
+
+console.log (binarySearch ([1, 2, 3, 4, 5, 8, 9], 8));
+console.log (binarySearch ([1, 2, 3, 4, 5, 8, 9], 7));
+```