algorithm for bfs searching

Java/Algorithm/SearchingAlgorithm/Breadth-First Search (BFS) Searching .java

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+import java.util.*;
+
+public class Graph {
+    private int V; // Number of vertices
+    private LinkedList<Integer> adj[]; // Adjacency List
+
+    // Constructor
+    Graph(int v) {
+        V = v;
+        adj = new LinkedList[v];
+        for (int i = 0; i < v; ++i)
+            adj[i] = new LinkedList();
+    }
+
+    // Add an edge to the graph
+    void addEdge(int v, int w) {
+        if (v >= 0 && v < V && w >= 0 && w < V) {
+            adj[v].add(w);
+        } else {
+            throw new IllegalArgumentException("Invalid edge: " + v + " -> " + w);
+        }
+    }
+
+    // BFS traversal from a given source s
+    void BFS(int s) {
+        // Mark all the vertices as not visited
+        boolean visited[] = new boolean[V];
+
+        // Create a queue for BFS
+        LinkedList<Integer> queue = new LinkedList<Integer>();
+
+        // Mark the current node as visited and enqueue it
+        visited[s] = true;
+        queue.add(s);
+
+        while (queue.size() != 0) {
+            // Dequeue a vertex from queue and print it
+            s = queue.poll();
+            System.out.print(s + " ");
+
+            // Get all adjacent vertices of the dequeued vertex s.
+            Iterator<Integer> i = adj[s].listIterator();
+            while (i.hasNext()) {
+                int n = i.next();
+                if (!visited[n]) {
+                    visited[n] = true;
+                    queue.add(n);
+                }
+            }
+        }
+    }
+
+    // Driver method to
+    public static void main(String args[]) {
+        Scanner scanner = new Scanner(System.in);
+
+        try {
+            System.out.print("Enter the number of vertices: ");
+            int V = scanner.nextInt();
+            if (V <= 0) {
+                throw new IllegalArgumentException("Number of vertices must be positive.");
+            }
+
+            Graph g = new Graph(V);
+
+            System.out.println("Enter the number of edges: ");
+            int E = scanner.nextInt();
+            if (E < 0) {
+                throw new IllegalArgumentException("Number of edges must be non-negative.");
+            }
+
+            System.out.println("Enter the edges (source destination): ");
+            for (int i = 0; i < E; i++) {
+                int source = scanner.nextInt();
+                int destination = scanner.nextInt();
+                g.addEdge(source, destination);
+            }
+
+            System.out.print("Enter the starting vertex for BFS: ");
+            int startVertex = scanner.nextInt();
+            if (startVertex < 0 || startVertex >= V) {
+                throw new IllegalArgumentException("Starting vertex is out of bounds.");
+            }
+
+            System.out.println("BFS Traversal starting from vertex " + startVertex + ":");
+            g.BFS(startVertex);
+        } catch (InputMismatchException e) {
+            System.out.println("Invalid input. Please enter integers only.");
+        } catch (IllegalArgumentException e) {
+            System.out.println(e.getMessage());
+        } finally {
+            scanner.close();
+        }
+    }
+}

Java/Algorithm/SortingAlgorithm/Bucket sort

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+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.InputMismatchException;
+import java.util.Scanner;
+
+public class BucketSort {
+    public static void bucketSort(double[] arr) {
+        int n = arr.length;
+        if (n <= 0) return;
+
+        // Create empty buckets
+        ArrayList<Double>[] buckets = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            buckets[i] = new ArrayList<>();
+        }
+
+        // Scatter the elements into the buckets
+        for (int i = 0; i < n; i++) {
+            int bucketIndex = (int) (n * arr[i]);
+            buckets[bucketIndex].add(arr[i]);
+        }
+
+        // Sort each bucket
+        for (int i = 0; i < n; i++) {
+            Collections.sort(buckets[i]);
+        }
+
+        // Concatenate the buckets
+        int index = 0;
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < buckets[i].size(); j++) {
+                arr[index++] = buckets[i].get(j);
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+
+        try {
+            System.out.print("Enter the number of elements: ");
+            int n = scanner.nextInt();
+            if (n <= 0) {
+                throw new IllegalArgumentException("Number of elements must be positive.");
+            }
+
+            double[] arr = new double[n];
+
+            System.out.println("Enter the elements (between 0 and 1): ");
+            for (int i = 0; i < n; i++) {
+                double element = scanner.nextDouble();
+                if (element < 0 || element > 1) {
+                    throw new IllegalArgumentException("Elements must be between 0 and 1.");
+                }
+                arr[i] = element;
+            }
+
+            System.out.println("Original array:");
+            printArray(arr);
+
+            bucketSort(arr);
+
+            System.out.println("Sorted array:");
+            printArray(arr);
+        } catch (InputMismatchException e) {
+            System.out.println("Invalid input. Please enter valid numbers.");
+        } catch (IllegalArgumentException e) {
+            System.out.println(e.getMessage());
+        } finally {
+            scanner.close();
+        }
+    }
+
+    public static void printArray(double[] arr) {
+        for (double value : arr) {
+            System.out.print(value + " ");
+        }
+        System.out.println();
+    }
+}

Java/Algorithm/SortingAlgorithm/Heap sort

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+import java.util.Arrays;
+import java.util.InputMismatchException;
+import java.util.Scanner;
+
+public class HeapSort {
+
+    // Function to perform heap sort
+    public static void heapSort(int[] arr) {
+        int n = arr.length;
+
+        // Build heap (rearrange array)
+        for (int i = n / 2 - 1; i >= 0; i--) {
+            heapify(arr, n, i);
+        }
+
+        // One by one extract an element from heap
+        for (int i = n - 1; i > 0; i--) {
+            // Move current root to end
+            int temp = arr[0];
+            arr[0] = arr[i];
+            arr[i] = temp;
+
+            // call max heapify on the reduced heap
+            heapify(arr, i, 0);
+        }
+    }
+
+    // To heapify a subtree rooted with node i which is an index in arr[]
+    public static void heapify(int[] arr, int n, int i) {
+        int largest = i; // Initialize largest as root
+        int l = 2 * i + 1; // left = 2*i + 1
+        int r = 2 * i + 2; // right = 2*i + 2
+
+        // If left child is larger than root
+        if (l < n && arr[l] > arr[largest]) {
+            largest = l;
+        }
+
+        // If right child is larger than largest so far
+        if (r < n && arr[r] > arr[largest]) {
+            largest = r;
+        }
+
+        // If largest is not root
+        if (largest != i) {
+            int swap = arr[i];
+            arr[i] = arr[largest];
+            arr[largest] = swap;
+
+            // Recursively heapify the affected sub-tree
+            heapify(arr, n, largest);
+        }
+    }
+
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+
+        try {
+            System.out.print("Enter the number of elements: ");
+            int n = scanner.nextInt();
+            if (n <= 0) {
+                throw new IllegalArgumentException("Number of elements must be positive.");
+            }
+
+            int[] arr = new int[n];
+
+            System.out.println("Enter the elements:");
+            for (int i = 0; i < n; i++) {
+                arr[i] = scanner.nextInt();
+            }
+
+            System.out.println("Original array: " + Arrays.toString(arr));
+
+            heapSort(arr);
+
+            System.out.println("Sorted array: " + Arrays.toString(arr));
+        } catch (InputMismatchException e) {
+            System.out.println("Invalid input. Please enter integers only.");
+        } catch (IllegalArgumentException e) {
+            System.out.println(e.getMessage());
+        } finally {
+            scanner.close();
+        }
+    }
+}

Java/Algorithm/SortingAlgorithm/radix sort

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+import java.util.Arrays;
+import java.util.InputMismatchException;
+import java.util.Scanner;
+
+public class RadixSort {
+
+    // Function to find the maximum element in the array
+    public static int getMax(int[] arr) {
+        int max = arr[0];
+        for (int i = 1; i < arr.length; i++) {
+            if (arr[i] > max) {
+                max = arr[i];
+            }
+        }
+        return max;
+    }
+
+    // A function to do counting sort of arr[] according to the digit represented by exp
+    public static void countSort(int[] arr, int exp) {
+        int n = arr.length;
+        int[] output = new int[n]; // output array
+        int[] count = new int[10];
+        Arrays.fill(count, 0);
+
+        // Store count of occurrences in count[]
+        for (int i = 0; i < n; i++) {
+            count[(arr[i] / exp) % 10]++;
+        }
+
+        // Change count[i] so that count[i] now contains actual position of this digit in output[]
+        for (int i = 1; i < 10; i++) {
+            count[i] += count[i - 1];
+        }
+
+        // Build the output array
+        for (int i = n - 1; i >= 0; i--) {
+            output[count[(arr[i] / exp) % 10] - 1] = arr[i];
+            count[(arr[i] / exp) % 10]--;
+        }
+
+        // Copy the output array to arr[], so that arr[] now contains sorted numbers according to the current digit
+        System.arraycopy(output, 0, arr, 0, n);
+    }
+
+    // The main function to that sorts arr[] of size n using Radix Sort
+    public static void radixSort(int[] arr) {
+        int max = getMax(arr);
+
+        // Do counting sort for every digit.
+        // Instead of passing digit number, exp is passed. exp is 10^i where i is the current digit number
+        for (int exp = 1; max / exp > 0; exp *= 10) {
+            countSort(arr, exp);
+        }
+    }
+
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+
+        try {
+            System.out.print("Enter the number of elements: ");
+            int n = scanner.nextInt();
+            if (n <= 0) {
+                throw new IllegalArgumentException("Number of elements must be positive.");
+            }
+
+            int[] arr = new int[n];
+
+            System.out.println("Enter the elements:");
+            for (int i = 0; i < n; i++) {
+                arr[i] = scanner.nextInt();
+            }
+
+            System.out.println("Original array: " + Arrays.toString(arr));
+
+            radixSort(arr);
+
+            System.out.println("Sorted array: " + Arrays.toString(arr));
+        } catch (InputMismatchException e) {
+            System.out.println("Invalid input. Please enter integers only.");
+        } catch (IllegalArgumentException e) {
+            System.out.println(e.getMessage());
+        } finally {
+            scanner.close();
+        }
+    }
+}