Update README.md

searching/README.md

@@ -102,3 +102,37 @@ def binary_search_matrix(matrix, item, lower=0, higher=None):
         
     return False
 ```
+
+<br>
+
+---
+
+### find the square root
+
+<br>
+
+```python
+
+def sqrt(x) -> int:
+    
+        if x < 2:
+            return x
+        
+        left, right = 2, x // 2
+        
+        while left <= right:
+            
+            mid = (right + left) // 2
+            num = mid * mid
+            
+            if num > x:
+                right = mid - 1
+                
+            elif num < x:
+                left = mid + 1
+                
+            else:
+                return mid
+            
+        return right
+```