Handling large input sizes in competitive programming requires careful attention to time complexity and algorithm design. Solutions with O(n^2) or worse complexity will often time out on large inputs. Instead, focus on algorithms with logarithmic or linear time complexity, such as binary search, divide-and-conquer, or dynamic programming with efficient state transitions. Preprocessing the input to reduce redundant calculations can also help, as can using efficient I/O methods to handle large datasets quickly. Understanding the problem’s constraints and choosing the right algorithm is essential for scaling your solution to large input sizes without running into time limits.