How Binary Search Algorithm Works and Time Complexity

How does a binary search algorithm work and its time complexity A binary search algorithm is an efficient method for finding a specific element in a sorted array. It works by repeatedly dividing the search interval in half until the target element is found or the interval becomes empty. Here's how it works and what its time complexity is: Binary Search Algorithm: 1. Start with the entire sorted array as the search interval. 2. Calculate the midpoint of the interval: (start + end) / 2. 3. Compare the midpoint element with the target element:  If they are equal, the search is successful, and the index of the element is returned.  If the midpoint element is greater than the target, narrow the interval to the lower half (before the midpoint).  If the midpoint element is less than the target, narrow the interval to the upper half (after the midpoint). 4. Repeat steps 2-3 until the interval becomes empty (start > end), indicating that the element is not in the array. Time Complexity: The time complexity of a binary search algorithm is logarithmic, specifically O(log n), where n is the number of elements in the array. This is because with each step, the search interval is halved, reducing the number of remaining elements to be searched exponentially. In other words, the algorithm eliminates half of the remaining possibilities in each step. This logarithmic behavior makes binary search highly efficient, especially for large datasets. For instance, if you have an array with 1 million elements, binary search would require around 20 comparisons to find the target element, whereas a linear search might require up to 1 million comparisons in the worst case. However, it's important to note that binary search is only applicable to sorted arrays. If the array is not sorted, you would need to sort it first, which usually has a time complexity of O(n log n) using efficient sorting algorithms like merge sort or quicksort. Here's why the time complexity is O(log n): In each step of the binary search, the search interval is halved. This means that with every comparison, the number of remaining elements to search through is reduced by half. Mathematically, this is similar to dividing "n" by 2 in each step: After 1 comparison: n / 2 elements left. After 2 comparisons: n / 4 elements left. After 3 comparisons: n / 8 elements left. And so on... As you can see, the number of remaining elements gets halved with each comparison. This behavior is characteristic of a logarithmic pattern. The base of the logarithm is 2 because we're halving the interval with each step. In the worst-case scenario, binary search continues until the search interval contains only one element or becomes empty. This worst-case scenario corresponds to the number of steps needed to reduce the interval to just one element (or none). If you have "n" elements, it takes approximately log₂(n) steps to get down to a single element or determine that the element is not present. Since the time complexity is expressed as O(log n), binary search remains efficient even for large datasets. This logarithmic behavior is what makes binary search a powerful algorithm for finding elements in sorted arrays.