run length encoding

Author: sushant

.classpath

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8">
+		<attributes>
+			<attribute name="owner.project.facets" value="java"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="output" path="build/classes"/>
+</classpath>

.gitignore

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+/build/

.project

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+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>HackerRank</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.wst.common.project.facet.core.builder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.wst.common.project.facet.core.nature</nature>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>

.settings/org.eclipse.jdt.core.prefs

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+eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.8
+org.eclipse.jdt.core.compiler.compliance=1.8
+org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
+org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
+org.eclipse.jdt.core.compiler.source=1.8

.settings/org.eclipse.wst.common.project.facet.core.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<faceted-project>
+  <installed facet="java" version="1.8"/>
+</faceted-project>

src/com/sushantjhingan/RunLengthEncoding.java

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+package com.sushantjhingan;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Scanner;
+
+
+/**
+ * Run-length encoding (RLE) is a very simple form of data compression in which runs of data 
+ * (that is, sequences in which the same data value occurs in many consecutive data elements) 
+ * are stored as a single data value and count, rather than as the original run. (Wikipedia)
+ * 
+ * @author Sushant Jhingan
+ *   Complexity O(n)
+ */
+public class RunLengthEncoding {
+	 
+    private static String method1(String input) {
+	    StringBuilder output = new StringBuilder();
+
+	    for (int i = 0, count = 1; i < input.length(); i++) {
+	        if (i + 1 < input.length() && input.charAt(i) == input.charAt(i + 1))
+	            count++;
+	        else {
+	            output = output.append(Integer.toString(count))
+	                    .append(Character.toString(input.charAt(i)));
+	            count = 1;
+	        }
+	    }
+	    return output.toString();
+	}
+	
+	
+    private static String method2(String source) {
+        StringBuffer dest = new StringBuffer();
+        for (int i = 0; i < source.length(); i++) {
+            int runLength = 1;
+            while(i+1 < source.length() && source.charAt(i) == (source.charAt(i+1))) 
+            {
+                runLength++;
+                i++;
+            }
+            
+            dest.append(source.charAt(i));
+            dest.append(runLength);
+        }
+        return dest.toString();
+    }
+    private static String method3(String input) {
+        
+        if(input.equals("") || input.trim().equals("")){
+            return "";
+        }
+        
+        Map<Character, Integer> map = new HashMap<Character, Integer>();
+        List<Character> list = new ArrayList<Character>();
+        for(int i=0;i<input.length();i++){
+            if(map.get(input.charAt(i)) != null){
+            	int count = map.get(input.charAt(i)) + 1;
+            	
+            	map.put(input.charAt(i), count);
+                
+            }else{
+            	map.put(input.charAt(i), 1);
+            	list.add(input.charAt(i));
+            }
+        }
+        StringBuilder builder = new StringBuilder();
+        for(Character s: list){
+        	builder.append(map.get(s));
+        	builder.append(s);
+        }
+
+        return builder.toString();
+    }
+    
+ 
+    public static void main(String[] args) {
+      Scanner scan = new Scanner(System.in);
+        String s = scan.nextLine();
+        System.out.println(method1(s));
+     
+    }
+}