GITBOOK-45: Basic binary search

SUMMARY.md

@@ -28,6 +28,7 @@
 
 ## Algorithms
 
+* [Binary Search](algorithms/binary-search.md)
 * [Sorting](algorithms/sorting.md)
 * [Greedy](algorithms/greedy.md)
 * [Dynamic Programming](algorithms/dynamic-programming.md)

algorithms/binary-search.md

@@ -0,0 +1,38 @@
+# Binary Search
+
+To search in a **sorted arrays**.
+
+#### Interactive 
+
+<pre class="language-python"><code class="lang-python"><strong>class Solution:
+</strong>    def iterative_binarys(self, nums: List[int], target: int):
+        p1, p2 = 0, len(nums) - 1
+        while(p2>=p1):
+            mid = p1 + ((p2-p1) // 2)
+            if target == nums[mid]:
+                return mid
+            elif target > nums[mid]:
+                p1 = mid+1
+            else:
+                p2 = mid-1
+        return -1
+</code></pre>
+
+#### Recursive
+
+```python
+class Solution:
+    def recursive_binarys(self, nums, target, left, right):
+        if left > right:
+            return -1
+        mid = left + ((right - left) // 2)
+        if nums[mid] == target:
+            return mid
+        elif nums[mid] > target:
+            return self.recursive_binarys(nums, target, left, mid-1)
+        else:
+            return self.recursive_binarys(nums, target, mid+1, right)
+```
+
+Note: Do not worry if it's an even numbered arrays, `mid` will reach there (as it checks even 1 length array `[a]` at the end)
+