Java Study 6-2주차

스케줄링 알고리즘 구현

1. FIFO(First In First Out)

public class FIFO {  
    public static void main(String[] args) throws IOException {  
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));  
        int n = Integer.parseInt(br.readLine());  
  
        Queue<Integer> start = new LinkedList<>();  
        Queue<Integer> time = new LinkedList<>();  
        for (int i = 0; i < n; i++) {  
            StringTokenizer st = new StringTokenizer(br.readLine());  
            start.add(Integer.valueOf(st.nextToken()));  
            time.add(Integer.valueOf(st.nextToken()));  
  
        }  
  
        int totalTime = 0;  
        while(!start.isEmpty()){  
            int nowStart = start.poll();  
            int nowTime = time.poll();  
            if(totalTime < nowStart){  //큐에 늦게 들어오는 경우 대기시간
                totalTime = nowStart;  
            }  
            totalTime = totalTime + nowTime;  
        }  
  
        System.out.println("총 걸린 시간 :" + totalTime);  
    }  
}

2. LIFO(Last In First Out)

public class LIFO {  
    public static void main(String[] args) throws IOException {  
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));  
        int n = Integer.parseInt(br.readLine());  
  
        int[][] jobs = new int[n][2];  
        boolean[] isClear = new boolean[n];  
        Stack<int[]> stack = new Stack<>();  
        for (int i = 0; i < n; i++) {  
            StringTokenizer st = new StringTokenizer(br.readLine());  
            jobs[i][0] = Integer.parseInt(st.nextToken());  
            jobs[i][1] = Integer.parseInt(st.nextToken());  
        }  
  
        int time = 0;  
        boolean isStackEnd = false;  
        boolean isJobEnd = false;  
        while(true){  
            if(isStackEnd && isJobEnd) break;  
            isJobEnd = true;  
            isStackEnd = false;  
            for (int i = 0; i < n; i++) {  
                if(jobs[i][0] <= time && !isClear[i]){  
                    int[] temp = new int[2];  
                    temp[0] = jobs[i][0];  
                    temp[1] = jobs[i][1];  
                    stack.add(temp);  
                    isClear[i] = true;  
                    isJobEnd = false;  
                    break;                }  
  
            }  
            for (int i = 0; i < n; i++) {  
                if(!isClear[i]){  
                    isJobEnd = false;  
                }  
            }  
            while(true){  
                if(stack.isEmpty()){  
                   isStackEnd = true;  
                   break;                }  
                int[] now = stack.pop();  
                if(now[1] == 0){  
                    continue;  
                }  
                now[1]--;  
                stack.add(now);  
  
                break;            }  
            time++;  
        }  
        System.out.println(time-1);  
  
    }  
}

RR(Round Robin)

 
public class RR {  
    public static void main(String[] args) throws IOException {  
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));  
        int n = Integer.parseInt(br.readLine());  
        int rrTime = Integer.parseInt(br.readLine());  
        boolean[] isClear = new boolean[n];  
  
        int[][] jobs = new int[n][2];  
        for (int i = 0; i < n; i++) {  
            StringTokenizer st = new StringTokenizer(br.readLine());  
            jobs[i][0] = Integer.parseInt(st.nextToken());  
            jobs[i][1] = Integer.parseInt(st.nextToken());  
        }  
  
        int time = 0;  
        boolean isFinish = false;  
        while(true){  
            boolean nothing = false;  
            if(isFinish) break;  
            for (int i = 0; i < n; i++) {  
                if(!isClear[i]){  
                    isFinish = false;  
                    break;                }  
                isFinish = true;  
            }  
            for (int i = 0; i < n; i++) {  
                if(jobs[i][0] > time) continue;  
                if(isClear[i]) continue;  
                if(jobs[i][1] < rrTime){  
                    time = time + jobs[i][1];  
                    isClear[i] = true;  
                    nothing = true;  
                    continue;                }  
                jobs[i][1] = jobs[i][1] - rrTime;  
                time = time + rrTime;  
                nothing = true;  
            }  
  
            if(!nothing){  
                time++;  
            }  
        }  
  
        System.out.println(time-1);  
    }  
}