Merge branch 'master' of gitlab.com:djdietrick/docs into master

docs/interview/ds/array.md

@@ -1,8 +1,8 @@
 # Arrays
 
-An array is a linear collection of data values that are accessible at numbered indices, starting at 0.  Arrays are stored in continguous memory.  There are two types of arrays, **static** and **dynamic**.  **Static** arrays are fixed length, meaning they will always take up the same amount of memory. 
+An array is a linear collection of data values that are accessible at numbered indices, starting at 0. Arrays are stored in continguous memory. There are two types of arrays, **static** and **dynamic**. **Static** arrays are fixed length, meaning they will always take up the same amount of memory.
 
-**Dynamic** arrays can change in size, and in statically typed languages like C++ there are called vectors.  **Dynamic** arrays allocate double the amount of memory you have specified to account for adding values to it.  When you reach a full array, then it allocates a new array with double the size and copies the values over which is an O(n) operation.
+**Dynamic** arrays can change in size, and in statically typed languages like C++ there are called vectors. **Dynamic** arrays allocate double the amount of memory you have specified to account for adding values to it. When you reach a full array, then it allocates a new array with double the size and copies the values over which is an O(n) operation.
 
 ## Complexity
 
@@ -15,4 +15,34 @@ An array is a linear collection of data values that are accessible at numbered i
 - Removing from middle: O(n)
 - Removing from end: O(1)
 - Copying: O(n)
-- Traversing (including mapping, filtering, etc): O(n)
+- Traversing (including mapping, filtering, etc): O(n)
+
+## Common Algorithms
+
+### Binary Search
+
+Binary search is useful when trying to find values in a sorted array. It works by picking a middle point to check, and then dividing the array in half based on whether the value is too big or small.
+
+```python
+def binarySearch(nums, target):
+    """
+    :type nums: List[int]
+    :type target: int
+    :rtype: int
+    """
+    if len(nums) == 0:
+        return -1
+
+    left, right = 0, len(nums) - 1
+    while left <= right:
+        mid = (left + right) // 2
+        if nums[mid] == target:
+            return mid
+        elif nums[mid] < target:
+            left = mid + 1
+        else:
+            right = mid - 1
+
+    # End Condition: left > right
+    return -1
+```