Complexity analysis is a crucial part of competitive programming because it allows you to evaluate the efficiency of your algorithm in terms of time and space. By analyzing the time complexity (how the runtime grows with input size) and space complexity (how much memory your solution uses), you can determine if your solution will meet the problem’s constraints. Problems often have strict time limits (e.g., 1 or 2 seconds), so understanding the complexity helps you avoid time limit exceeded (TLE) errors. Similarly, space complexity helps prevent memory limit exceeded (MLE) errors. Mastering complexity analysis is key to writing efficient, competitive code.