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Conversation avec Merlin louise.beaulieu992@gmail.com · Thu Aug 29 2024
Computing; could you explain BIG O notation to me, with an example?

Certainly! Big O notation is a way to describe the upper bound of the time complexity of an algorithm. It tells us how the running time of an algorithm scales as the input size increases.

The basic idea is to find the worst-case scenario for the algorithm, which means the maximum number of steps the algorithm will take as a function of the input size.

Here's an example to illustrate Big O notation:

Let's consider a simple algorithm that finds the maximum value in an array of integers:

python
def find_max(arr):
    max_val = arr[0]
    for i in range(1, len(arr)):
        if arr[i] > max_val:
            max_val = arr[i]
    return max_val
Open in:

In this algorithm, we start by assuming that the first element of the array is the maximum value. Then, we iterate through the rest of the array, comparing each element to the current maximum value. If we find a larger value, we update the maximum value.

The time complexity of this algorithm is O(n), where n is the size of the input array. This is because, in the worst case, we need to compare each element in the array to the current maximum value, which means the number of steps the algorithm takes is directly proportional to the size of the input.

Here's what the Big O notation means:

  • O(n): This means that the running time of the algorithm grows linearly with the size of the input. As the input size doubles, the running time also doubles.

Other common Big O notations include:

  • O(1): Constant time complexity, meaning the running time is the same regardless of the input size.
  • O(log n): Logarithmic time complexity, meaning the running time grows logarithmically with the input size.
  • O(n^2): Quadratic time complexity, meaning the running time grows quadratically with the input size.

Understanding Big O notation is important when analyzing the efficiency of algorithms, as it helps you compare the performance of different algorithms and make informed decisions about which one to use for a particular problem.