Algorithms

Author: Deepak Malik

src/com/deepak/algorithms/Advanced_Algorithms/Dijkstra_Shortest_Path.java

@@ -0,0 +1,5 @@
+package com.deepak.algorithms.Advanced_Algorithms;
+
+public class Dijkstra_Shortest_Path {
+
+}

…rithms/Advanced_Algorithms/Dijkstra.java …nced_Algorithms/Travelling_Salesman.javasrc/com/deepak/algorithms/Advanced_Algorithms/Dijkstra.java renamed to src/com/deepak/algorithms/Advanced_Algorithms/Travelling_Salesman.java src/com/deepak/algorithms/Advanced_Algorithms/Dijkstra.java renamed to src/com/deepak/algorithms/Advanced_Algorithms/Travelling_Salesman.java

@@ -1,5 +1,5 @@
 package com.deepak.algorithms.Advanced_Algorithms;
 
-public class Dijkstra {
+public class Travelling_Salesman {
 
 }

src/com/deepak/algorithms/Dynamic_Programming/Knapsack.java

@@ -0,0 +1,5 @@
+package com.deepak.algorithms.Dynamic_Programming;
+
+public class Knapsack {
+
+}

src/com/deepak/algorithms/Iterators/DFSForTree.java

@@ -0,0 +1,35 @@
+package com.deepak.algorithms.Iterators;
+
+import java.util.Stack;
+
+import com.deepak.algorithms.Library.TreeNode;
+
+public class DFSForTree {
+
+	public static void main(String[] args) {
+
+	}
+
+	public static void doPreOrder(TreeNode<Integer> root) {
+		Stack<TreeNode<Integer>> stack = new Stack<>();
+		stack.push(root);
+		TreeNode<Integer> current = root;
+		while (!stack.isEmpty() && current != null) {
+			TreeNode<Integer> itemOnTop = stack.pop();
+			System.out.println(itemOnTop + " ");
+			if (itemOnTop.hasLeft()) {
+				current = itemOnTop.left;
+			}
+		}
+		
+	}
+
+	public static void doInOrder(TreeNode<Integer> root) {
+
+	}
+
+	public static void doPostOrder(TreeNode<Integer> root) {
+
+	}
+
+}

src/com/deepak/algorithms/Iterators/InOrderIterator.java

@@ -0,0 +1,23 @@
+package com.deepak.algorithms.Iterators;
+
+import java.util.Iterator;
+
+public class InOrderIterator<T> implements Iterator<T> {
+
+	
+	@Override
+	public boolean hasNext() {
+		return false;
+	}
+
+	@Override
+	public T next() {
+		return null;
+	}
+
+	@Override
+	public void remove() {
+		throw new UnsupportedOperationException("Remove not supported!!");
+	}
+	
+}

src/com/deepak/algorithms/Iterators/PostOrderIterator.java

@@ -0,0 +1,7 @@
+package com.deepak.algorithms.Iterators;
+
+public class PostOrderIterator {
+
+	
+	
+}

src/com/deepak/algorithms/Recursion/Tower_Of_Hanoi.java

@@ -0,0 +1,5 @@
+package com.deepak.algorithms.Recursion;
+
+public class Tower_Of_Hanoi {
+
+}

src/com/deepak/algorithms/Regex/RegexForUSPhoneNumber.java

@@ -0,0 +1,32 @@
+package com.deepak.algorithms.Regex;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class RegexForUSPhoneNumber {
+	
+	public static void main(String[] args) {
+		System.out.println(matchUSPhoneNumber("425-633-6014"));
+		System.out.println(matchUSPhoneNumber("425-633-601"));
+		System.out.println(matchUSPhoneNumber("425-6336014"));
+		System.out.println(matchUSPhoneNumber("(425)-633-6014"));
+		System.out.println(matchUSPhoneNumber("42-33-6014"));
+		System.out.println(matchUSPhoneNumber("-633-6014"));
+		System.out.println(matchUSPhoneNumber("6014"));
+		System.out.println(matchUSPhoneNumber("425-633-60145"));
+	}
+	
+	/**
+	 * Method to match US phone number 
+	 * 
+	 * @param input
+	 * @return {@link boolean}
+	 */
+	public static boolean matchUSPhoneNumber(String input) {
+		String regexforPhone = "^\\(?([0-9]{3})\\)?[-.\\s]?([0-9]{3})[-.\\s]?([0-9]{4})$";
+		Pattern pattern = Pattern.compile(regexforPhone);
+		Matcher matcher = pattern.matcher(input);
+		return matcher.matches();
+	}
+
+}

src/com/deepak/algorithms/Regex/RegexIntroduction.md

@@ -0,0 +1,14 @@
+# Regex Introduction
+
+Regex is a sequence of characters that helps us to find a string or set of strings. Java provides java.util.regex package for pattern matching with regular expressions.
+There are 3 classes in this package,
+
+1. Pattern class - invoke compile() method alongwith the regex as param. This returns a pattern back.
+2. Matcher class - It interprets the pattern and matches it with given input.
+3. PatternSyntaxException class - Will be invoked if there exists a error in pattern.
+
+Capturing groups - 
+way to treat multiple characters as one single unit. Capturing groups are counted by number of open paranthesis
+in the regex.
+
+

src/com/deepak/algorithms/Sorting/MergeSort.java

@@ -17,7 +17,7 @@ public class MergeSort {
 	 * @param args
 	 */
 	public static void main(String[] args) {
-		int[] valuesToBeSorted = {7, 10, 47, 40, 83, 84, 65, 61, 32, 55, 49, 46, 25, 20, 93, 63, 54, 10};
+		int[] valuesToBeSorted = {7, 10, 47, 40};
 		System.out.println("******************* MERGE - SORT *******************");
 		int[] sortedValues = performMergeSort(valuesToBeSorted, 0, valuesToBeSorted.length - 1);
 		Arrays.stream(sortedValues).forEach(System.out::println);