If an algorithm takes the same amount of time to run, independent of the size of the input data, it is said to run in constant time. It is represented by O(1). Let's take the example of accessing the n^th element of an array. Regardless of the size of the array, it will take constant time to get the results. For example, the following function will return the first element of the array and has a complexity of O(1):

def getFirst(myList):
    return myList[0]

The output is shown as:

• Addition of a new element to a stack by using push or removing an element from a stack by using pop. Regardless of the size of the stack, it will take the same time to add or remove an element.
• Accessing the element of the hashtable (as discussed in Chapter 2, Data Structures Used in Algorithms).
• Bucket sort (as discussed in Chapter 2, Data Structures Used in Algorithms).