最小化完成任务所需时间：一种扫线算法教程

import java.util.*;

public class MinTaskTime {

    public static int minTimeToFinishTasks(List<List<Integer>> tasks) {
        List<int[]> events = new ArrayList<>();
        for (List<Integer> task : tasks) {
            int start = task.get(0);
            int end = task.get(1);
            int duration = task.get(2);
            events.add(new int[]{start, duration, 0}); // 0 for start
            events.add(new int[]{end, duration, 1});   // 1 for end
        }

        // Sort events by time, end events come first if times are equal
        Collections.sort(events, (a, b) -> {
            if (a[0] != b[0]) {
                return a[0] - b[0];
            } else {
                return a[2] - b[2]; // End events before start events
            }
        });

        Stack<int[]> activeTasks = new Stack<>();
        int totalTime = 0;

        for (int[] event : events) {
            int time = event[0];
            int duration = event[1];
            int type = event[2];

            if (type == 0) { // Start event
                activeTasks.push(new int[]{time, duration});
            } else { // End event
                int need = 0;
                // find the corresponding start event
                for(int i = 0; i < activeTasks.size(); i++){
                    int[] task = activeTasks.get(i);
                    if(task[0] == time && task[1] == duration){
                        need = task[1];
                        activeTasks.remove(i);
                        break;
                    }
                }

                totalTime += need;

                // Subtract time from other active tasks
                int subtract = need;
                for (int[] task : activeTasks) {
                    int reduce = Math.min(subtract, task[1]);
                    task[1] -= reduce;
                    subtract -= reduce;
                }

                // Clean up tasks with duration 0
                activeTasks.removeIf(task -> task[1] == 0);
            }
        }

        return totalTime;
    }

    public static void main(String[] args) {
        List<List<Integer>> tasks = new ArrayList<>();
        tasks.add(Arrays.asList(1, 3, 2));
        tasks.add(Arrays.asList(2, 5, 3));
        tasks.add(Arrays.asList(5, 6, 2));

        int minTime = minTimeToFinishTasks(tasks);
        System.out.println("Minimum time to finish all tasks: " + minTime); // Output: 4
    }
}