LeetCode 495: How to Calculate Total Poison Duration with Overlapping Intervals

LeetCode problem 495, rated Easy, asks developers to calculate the total time a character remains poisoned after multiple attacks, each lasting a fixed duration. When a new attack occurs before the current poison expires, the timer resets rather than stacking, meaning overlapping intervals must be handled carefully. A common mistake is overwriting the cumulative result inside a loop or assuming a single uniform overlap across all attack pairs. The correct approach adds the full duration for non-overlapping attacks and only the gap between consecutive attacks when an overlap exists. This greedy linear scan yields an O(n) time and O(1) space solution.