Binary search is one of the most important algorithms in competitive programming because it allows you to search sorted data in O(log n) time, which is much faster than linear search (O(n)). The basic idea is to repeatedly divide the search interval in half, comparing the middle element to the target value. If the middle element is greater than the target, you discard the right half; if it’s smaller, you discard the left half. This process continues until the target is found or the interval is empty. Binary search is widely used in problems involving searching, finding boundaries, or optimizing solutions.