SSTF Draft

package os_final_project;

import java.util.Arrays;
import java.util.Scanner;

public class SSTF {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.print("Enter the number of cylinders: ");
        int Cylinders = scanner.nextInt();

        System.out.print("Enter the starting head position: ");
        int headStart = scanner.nextInt();

        scanner.nextLine(); // consume newline character left in input stream

        int[] requests = null;
        boolean validInput = false;
        while (!validInput) {
            System.out.print("Enter the disk requests separated by spaces: ");
            String requestsInput = scanner.nextLine();
            String[] requestStrings = requestsInput.split(" ");
            requests = new int[requestStrings.length];
            validInput = true;
            for (int i = 0; i < requestStrings.length; i++) {
                try {
                    int request = Integer.parseInt(requestStrings[i]);
                    if (request < 0 || request >= Cylinders) {
                        System.out.println("Error: Request " + request + " is out of range [0, " + (Cylinders-1) + "]");
                        validInput = false;
                        break;
                    }
                    requests[i] = request;
                } catch (NumberFormatException e) {
                    System.out.println("Error: Invalid request format: " + requestStrings[i]);
                    validInput = false;
                    break;
                }
            }
        }
        int[] traversalPath = calculateTraversalPath(headStart, requests);
        int seekTime = calculateShortestSeekTime(headStart, requests);
        printTraversalPath(traversalPath);
        System.out.println("Total head movement: " + seekTime);
        
        
    }

    public static int calculateShortestSeekTime(int headStart, int[] requests) {
        int totalSeekTime = 0;
        int currentPosition = headStart;
        int numRequests = requests.length;

        boolean[] visited = new boolean[numRequests];
        for (int i = 0; i < numRequests; i++) {
            int shortestDistance = Integer.MAX_VALUE;
            int shortestIndex = -1;

            for (int j = 0; j < numRequests; j++) {
                if (!visited[j]) {
                    int distance = Math.abs(requests[j] - currentPosition);
                    if (distance < shortestDistance) {
                        shortestDistance = distance;
                        shortestIndex = j;
                    }
                }
            }

            visited[shortestIndex] = true;
            totalSeekTime += shortestDistance;
            currentPosition = requests[shortestIndex];
        }

        return totalSeekTime;
    }


    public static int[] calculateTraversalPath(int headStart, int[] requests) {
        int numRequests = requests.length;
        int[] traversalPath = new int[numRequests + 1];
        traversalPath[0] = headStart;

        boolean[] visited = new boolean[numRequests];
        for (int i = 0; i < numRequests; i++) {
            int shortestDistance = Integer.MAX_VALUE;
            int shortestIndex = -1;

            for (int j = 0; j < numRequests; j++) {
                if (!visited[j]) {
                    int distance = Math.abs(requests[j] - traversalPath[i]);
                    if (distance < shortestDistance || (distance == shortestDistance && j < shortestIndex)) {
                        shortestDistance = distance;
                        shortestIndex = j;
                    }
                }
            }

            visited[shortestIndex] = true;
            traversalPath[i + 1] = requests[shortestIndex];
        }

        return traversalPath;
    }



    public static void printTraversalPath(int[] traversalPath) {
        System.out.print("Traversal path: ");
        for (int i = 0; i < traversalPath.length - 1; i++) {
            int currentNode = traversalPath[i];
            int nextNode = traversalPath[i+1];
            int seekTime = Math.abs(nextNode - currentNode);
            System.out.println(currentNode + " -> " + nextNode + " [" + seekTime + "], ");
        }
        System.out.println(traversalPath[traversalPath.length-1]);
    }
       

}