Hactoberfest 2024 Contribution

src/test/java/com/thealgorithms/operatingsystemconcepts/BankersAlgorithm.java

@@ -0,0 +1,160 @@
+package com.thealgorithms.operatingsystemconcepts;
+
+import java.util.Arrays;
+import java.util.Scanner;
+
+public class BankersAlgorithm {
+    private int processes; // Number of processes
+    private int resources; // Number of resources
+    private int[] available; // Available instances of each resource
+    private int[][] max; // Maximum R of each resource
+    private int[][] allot; // Allocation R of each resource
+    private int[][] need; // Remaining R needed by each process
+
+    public BankersAlgorithm(int processes, int resources) {
+        this.processes = processes;
+        this.resources = resources;
+        available = new int[resources];
+        max = new int[processes][resources];
+        allot = new int[processes][resources];
+        need = new int[processes][resources];
+    }
+
+    // Function to calculate the need matrix
+    private void calculateNeed() {
+        for (int i = 0; i < processes; i++) {
+            for (int j = 0; j < resources; j++) {
+                need[i][j] = max[i][j] - allot[i][j];
+            }
+        }
+    }
+
+    // Function to find if the system is in a safe state
+    private boolean isSafe() {
+        boolean[] finish = new boolean[processes];
+        int[] safeSequence = new int[processes];
+        int count = 0;
+
+        int[] work = Arrays.copyOf(available, resources);
+
+        while (count < processes) {
+            boolean found = false;
+
+            for (int p = 0; p < processes; p++) {
+                if (!finish[p]) {
+                    int j;
+                    for (j = 0; j < resources; j++) {
+                        if (need[p][j] > work[j]) {
+                            break;
+                        }
+                    }
+
+                    if (j == resources) {
+                        for (int k = 0; k < resources; k++) {
+                            work[k] += allot[p][k];
+                        }
+                        safeSequence[count++] = p;
+                        finish[p] = true;
+                        found = true;
+                    }
+                }
+            }
+
+            if (!found) {
+                System.out.println("System is not in a safe state.");
+                return false;
+            }
+        }
+
+        System.out.println("System is in a safe state.");
+        System.out.print("Safe sequence is: ");
+        for (int i = 0; i < processes; i++) {
+            System.out.print(safeSequence[i] + " ");
+        }
+        System.out.println();
+        return true;
+    }
+
+    // Function to request resources
+    public void requestResources(int processNum, int[] request) {
+        // Check if request is less than need
+        for (int i = 0; i < resources; i++) {
+            if (request[i] > need[processNum][i]) {
+                System.out.println("Error: Process has exceeded its maximum claim.");
+                return;
+            }
+        }
+
+        // Check if request is less than available
+        for (int i = 0; i < resources; i++) {
+            if (request[i] > available[i]) {
+                System.out.println("Process is waiting.");
+                return;
+            }
+        }
+
+        // Pretend to allocate resources
+        for (int i = 0; i < resources; i++) {
+            available[i] -= request[i];
+            allot[processNum][i] += request[i];
+            need[processNum][i] -= request[i];
+        }
+
+        // Check system state
+        if (isSafe()) {
+            System.out.println("Resources allocated successfully.");
+        } else {
+            // Rollback
+            for (int i = 0; i < resources; i++) {
+                available[i] += request[i];
+                allot[processNum][i] -= request[i];
+                need[processNum][i] += request[i];
+            }
+            System.out.println("Resources allocation leads to unsafe state, request denied.");
+        }
+    }
+
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+
+        System.out.print("Enter number of processes: ");
+        int processes = scanner.nextInt();
+        System.out.print("Enter number of resources: ");
+        int resources = scanner.nextInt();
+
+        BankersAlgorithm bankersAlgorithm = new BankersAlgorithm(processes, resources);
+
+        System.out.println("Enter maximum resource matrix:");
+        for (int i = 0; i < processes; i++) {
+            for (int j = 0; j < resources; j++) {
+                bankersAlgorithm.max[i][j] = scanner.nextInt();
+            }
+        }
+
+        System.out.println("Enter allocation matrix:");
+        for (int i = 0; i < processes; i++) {
+            for (int j = 0; j < resources; j++) {
+                bankersAlgorithm.allot[i][j] = scanner.nextInt();
+            }
+        }
+
+        System.out.println("Enter available resources:");
+        for (int i = 0; i < resources; i++) {
+            bankersAlgorithm.available[i] = scanner.nextInt();
+        }
+
+        bankersAlgorithm.calculateNeed();
+
+        System.out.print("Request resources for process (0 to " + (processes - 1) + "): ");
+        int processNum = scanner.nextInt();
+        System.out.println("Enter request:");
+        int[] request = new int[resources];
+        for (int i = 0; i < resources; i++) {
+            request[i] = scanner.nextInt();
+        }
+
+        bankersAlgorithm.requestResources(processNum, request);
+
+        scanner.close();
+    }
+}