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Algorithms Added
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‎Algorithms/Algorithms.iml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<module type="JAVA_MODULE" version="4">
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<component name="NewModuleRootManager" inherit-compiler-output="true">
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<exclude-output />
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<content url="file://$MODULE_DIR$">
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<sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
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</content>
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<orderEntry type="inheritedJdk" />
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<orderEntry type="sourceFolder" forTests="false" />
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</component>
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</module>

‎Algorithms/src/BfsAlgorithm.java‎

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import java.util.*;
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class BfsAlgorithm {
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public static void main(String[] args) {
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int n = 15;
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List<Edge> nodes = Arrays.asList(new Edge(1, 2), new Edge(1, 3), new Edge(1, 4), new Edge(2, 5), new Edge(2, 6), new Edge(4, 7), new Edge(4, 8), new Edge(5, 9), new Edge(5, 10), new Edge(7, 12), new Edge(7, 12));
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Graph graph = new Graph(nodes, n);
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boolean[] visitors = new boolean[n];
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Queue<Integer> q = new ArrayDeque<>();
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for (int i = 0; i < n; i++) {
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if (!visitors[i]) {
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visitors[i] = true;
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q.add(i);
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bfsImplementation(graph, q, visitors);
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}
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}
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}
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private static void bfsImplementation(Graph graph, Queue<Integer> q, boolean[] visitors) {
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if (q.isEmpty()) return;
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int nodeIndex = q.poll();
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System.out.print(nodeIndex + " ");
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for (int node : graph.adjList.get(nodeIndex)) {
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if (!visitors[node]) {
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visitors[node] = true;
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q.add(node);
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}
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}
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bfsImplementation(graph, q, visitors);
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}
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}
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class Edge {
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int src, dest;
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public Edge(int src, int dest) {
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this.src = src;
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this.dest = dest;
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}
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}
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class Graph {
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List<List<Integer>> adjList;
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public Graph(List<Edge> nodes, int n) {
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this.adjList = new ArrayList<>();
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for (int i = 0; i < n; i++) {
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adjList.add(new ArrayList<>());
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}
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for (Edge node : nodes) {
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int src = node.src;
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int dest = node.dest;
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adjList.get(src).add(dest);
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adjList.get(dest).add(src);
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}
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}
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}

‎Algorithms/src/BfsProblems.java‎

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import java.util.*;
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class BfsProblems {
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public static void main(String[] args) {
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Node root = new Node(1);
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root.left = new Node(2);
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root.right = new Node(3);
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root.left.right = new Node(4);
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root.right.left = new Node(5);
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root.right.right = new Node(6);
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root.right.left.left = new Node(7);
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root.right.left.right = new Node(8);
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// findAllRightNodes(root);
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// System.out.println("Min Depth Value is = " + findMinDepth(root));
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// printTree(root);
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printNodes(root);
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}
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private static void printTree(Node node) {
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HashMap<Integer, ArrayList<Integer>> treeMap = new HashMap<>();
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mapTreeLevels(node, treeMap, 1);
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LinkedList<List<Integer>> reverseLevel = new LinkedList<>();
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// Top to Bottom
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treeMap.forEach((level, nodeValues) -> {
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System.out.print(treeMap.get(level));
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reverseLevel.addFirst(treeMap.get(level));
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});
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System.out.println();
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// Bottom To Top
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reverseLevel.forEach(System.out::print);
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}
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public static void insertIntoMultiMap(Map<Integer, List<Integer>> map,
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Integer key, Integer value) {
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map.putIfAbsent(key, new ArrayList<>());
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map.get(key).add(value);
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}
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public static void printNodes(Node node) {
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if (node == null) return;
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int level = 1;
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Map<Integer, List<Integer>> map = new HashMap<>();
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insertIntoMultiMap(map, level, node.getData());
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Queue<Node> q1 = new ArrayDeque<>(), q2 = new ArrayDeque<>();
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if (node.left != null && node.right != null) {
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q1.add(node.left);
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q2.add(node.right);
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}
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while (!q1.isEmpty()) {
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level++;
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int n = q1.size();
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while (n-- > 0) {
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Node x = q1.poll();
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if (x != null) {
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insertIntoMultiMap(map, level, x.getData());
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if (x.left != null) q1.add(x.left);
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if (x.right != null) q1.add(x.right);
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}
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Node y = q2.poll();
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if (y != null) {
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map.get(level).add(y.getData());
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if (y.right != null) q2.add(y.right);
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if (y.left != null) q2.add(y.left);
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}
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}
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}
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for (int i = map.size(); i > 0; i--) {
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System.out.print(map.get(i));
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}
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}
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private static void mapTreeLevels(Node node, HashMap<Integer, ArrayList<Integer>> treeMap, int level) {
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if (node == null) return;
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ArrayList<Integer> nodes = new ArrayList<>();
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if (treeMap.containsKey(level)) nodes = treeMap.get(level);
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nodes.add(node.getData());
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treeMap.put(level, nodes);
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mapTreeLevels(node.left, treeMap, level + 1);
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mapTreeLevels(node.right, treeMap, level + 1);
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}
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private static int findMinDepth(Node node) {
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if (node == null) return 0;
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int l = findMinDepth(node.left);
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int r = findMinDepth(node.right);
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if (node.left == null) return r + 1;
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if (node.right == null) return l + 1;
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return Math.min(l, r) + 1;
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}
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private static void findAllRightNodes(Node root) {
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Map<Integer, Integer> rightNodes = new HashMap<>();
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printAllRightNodes(rightNodes, 1, root);
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rightNodes.forEach((level, rightNode) -> System.out.print(rightNode + " "));
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}
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private static void printAllRightNodes(Map<Integer, Integer> rightNodes, int level, Node root) {
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if (root == null) return;
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// Add this condition to get left view of tree:
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// if (!rightNodes.containsKey(level))
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rightNodes.put(level, root.getData());
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printAllRightNodes(rightNodes, level + 1, root.left);
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printAllRightNodes(rightNodes, level + 1, root.right);
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}
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}
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class Node {
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private final int data;
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Node left, right;
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Node(int data) {
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this.data = data;
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this.left = this.right = null;
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}
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public int getData() {
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return this.data;
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}
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}

‎Algorithms/src/DfsAlgorithm.java‎

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import java.util.Arrays;
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import java.util.List;
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class DfsAlgorithm {
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public static void DFS(Graph graph, int v, boolean[] discovered) {
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discovered[v] = true;
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System.out.print(v + " ");
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for (int u : graph.adjList.get(v)) {
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if (!discovered[u]) {
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DFS(graph, u, discovered);
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}
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}
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}
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public static void main(String[] args) {
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List<Edge> edges = Arrays.asList(
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new Edge(1, 2), new Edge(1, 7), new Edge(1, 8), new Edge(2, 3),
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new Edge(2, 6), new Edge(3, 4), new Edge(3, 5), new Edge(8, 9),
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new Edge(8, 12), new Edge(9, 10), new Edge(9, 11)
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);
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int n = 13;
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Graph graph = new Graph(edges, n);
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boolean[] discovered = new boolean[n];
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for (int i = 0; i < n; i++) {
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if (!discovered[i]) {
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DFS(graph, i, discovered);
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}
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}
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}
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}

‎Algorithms/src/countNumberOfIsland.java‎

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public class countNumberOfIsland {
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static int[] moveX = {-1, -1, 0, 1, 1, 1, -1, 0}, moveY = {0, 1, 1, 1, 0, -1, -1, -1};
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static int Rows, Cols;
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public static void main(String[] args) {
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int[][] islandGrid = new int[][]{
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{1, 0, 1, 0, 0, 0, 1, 1, 1, 1},
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{0, 0, 1, 0, 1, 0, 1, 0, 0, 0},
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{1, 1, 1, 1, 0, 0, 1, 0, 0, 0},
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{1, 0, 0, 1, 0, 1, 0, 0, 0, 0},
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{1, 1, 1, 1, 0, 0, 0, 1, 1, 1},
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{0, 1, 0, 1, 0, 0, 1, 1, 1, 1},
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{0, 0, 0, 0, 0, 1, 1, 1, 0, 0},
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{0, 0, 0, 1, 0, 0, 1, 1, 1, 0},
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{1, 0, 1, 0, 1, 0, 0, 1, 0, 0},
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{1, 1, 1, 1, 0, 0, 0, 1, 1, 1}
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};
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Rows = islandGrid.length;
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Cols = islandGrid[0].length;
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System.out.println("No of Islands: " + countNumberOfIsland.numIslands(islandGrid));
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}
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public static int numIslands(int[][] islandGrid) {
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if (Rows == 0) return 0;
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int result = 0;
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for (int i = 0; i < Rows; i++) {
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for (int j = 0; j < Cols; j++) {
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if (islandGrid[i][j] == 1) {
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DFS(islandGrid, i, j);
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result++;
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}
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}
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}
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return result;
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}
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public static void DFS(int[][] islandGrid, int row, int col) {
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if (row < 0 || col < 0 || row >= Rows || col >= Cols || islandGrid[row][col] != 1)
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return;
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islandGrid[row][col] = 0;
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for (int i = 0; i < 8; i++) {
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DFS(islandGrid, row + moveX[i], col + moveY[i]);
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}
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}
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}

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