Explain how does the Sentinel Search work?

The Sentinel Search, also known as the Sentinel Linear Search, is a variation of the linear search algorithm used to find the position of a target value in an array. It improves the efficiency of the search by eliminating the need for an explicit comparison in each iteration of the loop.

Here’s how the Sentinel Search algorithm works:

  1. Initialization:
    • Add a sentinel value at the end of the array, which is equal to the target value being searched.
    • Save the original value at the last position of the array to restore it later.
  2. Search Process:
    • Start iterating through the array from the first element.
    • In each iteration, compare the current element with the target value.
    • If the target value is found (i.e., the current element matches the target value), the loop can be terminated, and the position of the target is returned.
    • If the current element does not match the target value, move to the next element.
  3. Termination:
    • The loop terminates when the sentinel value is encountered.
    • Since the sentinel value is guaranteed to match the target value, there is no need for an explicit comparison in each iteration of the loop.
    • If the loop reaches the sentinel value without finding the target value, it means the target value is not present in the array. In this case, the algorithm returns a special value (e.g., -1) to indicate the absence of the target.

The Sentinel Search algorithm reduces the number of conditional checks required during the search process, as the sentinel value ensures a match is eventually found. This eliminates the need for an explicit comparison within the loop, resulting in improved efficiency compared to traditional linear search algorithms.

It’s important to note that the Sentinel Search is most effective when the target value is likely to be found within the array. If the target value is not present, the algorithm still performs the same number of iterations as in a regular linear search.

Overall, the Sentinel Search is a simple yet efficient variation of the linear search algorithm that eliminates the need for a conditional check in each iteration, resulting in improved performance for searching a target value in an array.

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