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split strings with backtracking

I'm trying to write a code that split a spaceless string into meaningful words but when I give sentence like "arealways" it returns ['a', 'real', 'ways'] and what I want is ['are', 'always'] and my dictionary contains all this words. How can I can write a code that keep backtracking till find the best matching?
the code that returns 'a', 'real', 'ways':
splitter.java:
public class splitter {
HashMap<String, String> map = new HashMap<>();
Trie dict;
public splitter(Trie t) {
dict = t;
}
public String split(String test) {
if (dict.contains(test)) {
return (test);
} else if (map.containsKey(test)) {
return (map.get(test));
} else {
for (int i = 0; i < test.length(); i++) {
String pre = test.substring(0, i);
if (dict.contains(pre)) {
String end = test.substring(i);
String fixedEnd = split(end);
if(fixedEnd != null){
map.put(test, pre + " " + fixedEnd);
return pre + " " + fixedEnd;
}else {
}
}
}
}
map.put(test,null);
return null;
}
}
Trie.java:
public class Trie {
public static class TrieNode {
private HashMap<Character, TrieNode> charMap = new HashMap<>();
public char c;
public boolean endOWord;
public void insert(String s){
}
public boolean contains(String s){
return true;
}
}
public TrieNode root;
public Trie() {
root = new TrieNode();
}
public void insert(String s){
TrieNode p = root;
for(char c : s.toCharArray()) {
if(! p.charMap.containsKey(c)) {
TrieNode node = new TrieNode();
node.c = c;
p.charMap.put(c, node);
}
p = p.charMap.get(c);
}
p.endOWord = true;
}
public boolean contains(String s){
TrieNode p = root;
for(char c : s.toCharArray()) {
if(!p.charMap.containsKey(c)) {
return false;
}
p = p.charMap.get(c);
}
return p.endOWord;
}
public void insertDictionary(String filename) throws FileNotFoundException{
File file = new File(filename);
Scanner sc = new Scanner(file);
while(sc.hasNextLine())
insert(sc.nextLine());
}
public void insertDictionary(File file) throws FileNotFoundException{
Scanner sc = new Scanner(file);
while(sc.hasNextLine())
insert(sc.nextLine());
}
}
WordSplitter class:
public class WordSplitter {
public static void main(String[] args) throws FileNotFoundException {
String test = "arealways";
String myFile = "/Users/abc/Desktop/dictionary.txt";
Trie dict = new Trie();
dict.insertDictionary(myFile);
splitter sp = new splitter(dict);
test = sp.split(test);
if(test != null)
System.out.println(test);
else
System.out.println("No Splitting Found.");
}
}

Using the OP's split method and the implementation of Trie found in The Trie Data Structure in Java Baeldung's article, I was able to get the following results:
realways=real ways
arealways=a real ways
However, if I remove the word "real" or "a" from the dictionary, I get the following results:
realways=null
arealways=are always
Here's the entire code I used to get these results:
public class Splitter {
private static Map<String, String> map = new HashMap<>();
private Trie dict;
public Splitter(Trie t) {
dict = t;
}
/**
* #param args
*/
public static void main(String[] args) {
List<String> words = List.of("a", "always", "are", "area", "r", "way", "ways"); // The order of these words does not seem to impact the final result
String test = "arealways";
Trie t = new Trie();
for (String word : words) {
t.insert(word);
}
System.out.println(t);
Splitter splitter = new Splitter(t);
splitter.split(test);
map.entrySet().forEach(System.out::println);
}
public String split(String test) {
if (dict.find(test)) {
return (test);
} else if (map.containsKey(test)) {
return (map.get(test));
} else {
for (int i = 0; i < test.length(); i++) {
String pre = test.substring(0, i);
if (dict.find(pre)) {
String end = test.substring(i);
String fixedEnd = split(end);
if (fixedEnd != null) {
map.put(test, pre + " " + fixedEnd);
return pre + " " + fixedEnd;
} else {
}
}
}
}
map.put(test, null);
return null;
}
public static class Trie {
private TrieNode root = new TrieNode();
public boolean find(String word) {
TrieNode current = root;
for (int i = 0; i < word.length(); i++) {
char ch = word.charAt(i);
TrieNode node = current.getChildren().get(ch);
if (node == null) {
return false;
}
current = node;
}
return current.isEndOfWord();
}
public void insert(String word) {
TrieNode current = root;
for (char l : word.toCharArray()) {
current = current.getChildren().computeIfAbsent(l, c -> new TrieNode());
}
current.setEndOfWord(true);
}
#Override
public String toString() {
return toString(root);
}
/**
* #param root2
* #return
*/
private String toString(TrieNode node) {
return node.toString();
}
public static class TrieNode {
private Map<Character, TrieNode> children = new HashMap<>() ;
private String contents;
private boolean endOfWord;
public Map<Character, TrieNode> getChildren() {
return children;
}
public void setEndOfWord(boolean endOfWord) {
this.endOfWord = endOfWord;
}
public boolean isEndOfWord() {
return endOfWord;
}
#Override
public String toString() {
StringBuilder sbuff = new StringBuilder();
if (isLeaf()) {
return sbuff.toString();
}
children.entrySet().forEach(entry -> {
sbuff.append(entry.getKey() + "\n");
});
sbuff.append(" ");
return children.toString();
}
private boolean isLeaf() {
return children.isEmpty();
}
}
public void delete(String word) {
delete(root, word, 0);
}
private boolean delete(TrieNode current, String word, int index) {
if (index == word.length()) {
if (!current.isEndOfWord()) {
return false;
}
current.setEndOfWord(false);
return current.getChildren().isEmpty();
}
char ch = word.charAt(index);
TrieNode node = current.getChildren().get(ch);
if (node == null) {
return false;
}
boolean shouldDeleteCurrentNode = delete(node, word, index + 1) && !node.isEndOfWord();
if (shouldDeleteCurrentNode) {
current.getChildren().remove(ch);
return current.getChildren().isEmpty();
}
return false;
}
}
}
I improved the original code by adding a toString() method to the Trie and TrieNode. Now, when I print out the Trie object "t", I get the following result:
{a={r={e={a=}}, l={w={a={y={s=}}}}}, w={a={y={s=}}}}
My conclusion is that the OP's TrieNode implementation is incorrect. The way the Trie is built, given the inputted string value, the behavior described by the OP seems to be correct.

Modifying Dijkstra to save paths with equal values - StackOverflow error

I'm trying to modify Dijkstra's algorithm to show all the paths that have the minimum value. So I decided to use a list of previous vertices. And I added an if clause that checks if the path is igual to the previous with minimum value I add the previous vertex as the parent of the current one.
The problem is that I am getting a StackOverflow error and I don't know what is causing it.
This is my code:
The purpose of the code below is to calculate Dijkstra for all of the vertices in the graph, calculate the number of times a vertex appears in the minimum paths found and display in decrescent order the all of them.
public class Dijkstra {
public static final Map<String, Integer> ordem = new HashMap<>();
public static void main(String[] args) throws FileNotFoundException, IOException {
List<Graph.Edge> edges = new ArrayList<>();
try {
FileReader arq = new FileReader("input.txt");
BufferedReader fw = new BufferedReader(arq);
String linha = "";
while (fw.ready()) {
linha = fw.readLine();
if (!linha.equals("0,0,0")) {
String parts[] = linha.split(",");
ordem.put(parts[0], 0);
ordem.put(parts[1], 0);
Graph.Edge a = new Graph.Edge(parts[0], parts[1], 100 - Integer.parseInt(parts[2]));
edges.add(a);
} else {
break;
}
}
fw.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
Graph g = new Graph(edges);
for (int i = 0; i < 5; i++) {
g.dijkstra(String.valueOf(i));
g.printAllPaths();
}
Object[] a = ordem.entrySet().toArray();
Arrays.sort(a, new Comparator() {
public int compare(Object o1, Object o2) {
return ((Map.Entry<String, Integer>) o2).getValue()
.compareTo(((Map.Entry<String, Integer>) o1).getValue());
}
});
for (Object e : a) {
System.out.print(((Map.Entry<String, Integer>) e).getKey() + " ");
}
System.out.println("\n");
}
}
class Graph {
private final Map<String, Vertex> graph;
public static class Edge {
public final String v1, v2;
public final int dist;
public Edge(String v1, String v2, int dist) {
this.v1 = v1;
this.v2 = v2;
this.dist = dist;
}
}
public static class Vertex implements Comparable<Vertex> {
public final String name;
public int dist = Integer.MAX_VALUE;
public List<Vertex> previous = new ArrayList<>();
public final Map<Vertex, Integer> neighbours = new HashMap<>();
public Vertex(String name) {
this.name = name;
}
private void printPath() {
if (this == this.previous) {
} else if (this.previous == null) {
} else {
//This is where I am getting the error
for (int i = 0; i<this.previous.size(); i++){
this.previous.get(i).printPath();
Dijkstra.ordem.replace(this.name, Dijkstra.ordem.get(this.name) + 1);
}
}
}
public int compareTo(Vertex other) {
if (dist == other.dist) {
return name.compareTo(other.name);
}
return Integer.compare(dist, other.dist);
}
#Override
public String toString() {
return "(" + name + ", " + dist + ")";
}
}
public Graph(List<Graph.Edge> edges) {
graph = new HashMap<>(edges.size());
for (Edge e : edges) {
if (!graph.containsKey(e.v1)) {
graph.put(e.v1, new Vertex(e.v1));
}
if (!graph.containsKey(e.v2)) {
graph.put(e.v2, new Vertex(e.v2));
}
}
for (Edge e : edges) {
graph.get(e.v1).neighbours.put(graph.get(e.v2), e.dist);
graph.get(e.v2).neighbours.put(graph.get(e.v1), e.dist);
}
}
public void dijkstra(String startName) {
if (!graph.containsKey(startName)) {
System.err.printf("Graph doesn't contain start vertex \"%s\"\n", startName);
return;
}
final Vertex source = graph.get(startName);
NavigableSet<Vertex> q = new TreeSet<>();
// Inicializacao dos vertices
for (Vertex v : graph.values()) {
//v.previous = v == source ? list : null;
if (v == source) {
v.previous.add(source);
} else {
v.previous = new ArrayList<>();
}
v.dist = v == source ? 0 : Integer.MAX_VALUE;
q.add(v);
}
dijkstra(q);
}
private void dijkstra(final NavigableSet<Vertex> q) {
Vertex u, v;
while (!q.isEmpty()) {
u = q.pollFirst();
if (u.dist == Integer.MAX_VALUE) {
}
for (Map.Entry<Vertex, Integer> a : u.neighbours.entrySet()) {
v = a.getKey();
final int alternateDist = u.dist + a.getValue();
if (alternateDist < v.dist) {
q.remove(v);
v.dist = alternateDist;
v.previous.add(u);
q.add(v);
} else if(alternateDist == v.dist) {
v.previous.add(u);
}
}
}
}
public void printPath(String endName) {
if (!graph.containsKey(endName)) {
System.err.printf("Graph doesn't contain end vertex \"%s\"\n", endName);
return;
}
graph.get(endName).printPath();
//System.out.println();
}
public void printAllPaths() {
for (Vertex v : graph.values()) {
v.printPath();
}
}
}
This is the error:
Exception in thread "main" java.lang.StackOverflowError
at Graph$Vertex.printPath(Dijkstra.java:117)
at Graph$Vertex.printPath(Dijkstra.java:118)

As the Error message already suggests: Your dijkstra isn't the problem.
The problem is printPath() calling itself.
Likely the culprit is
if (this == this.previous) {} ...
You compare Vertex this to List<Vertex> previous. Maybe you want to check
if (this == this.previous.get(this.previous.size() - 1)) {} ...
instead.
I didn't test this, because your code is (1.) too long and (2.) not self-contained (missing at least "input.txt").

Building a tree from string input

I am stuck at the logic as for how to generate a tree when a string input is provided . Such as when i have a input of following form -
(1 (2 (3) (4)) (5 (6) ())
Representing tree will be like so -
1
/ \
2 5
/ \ /\
3 4 6 ()
I can build tree from usual like tree.add(data) and then looking for the new node to be self added by judging if its greater or smaller than parent node . But i am not able to understand how to implement how to store above the above mention string in binary data structure form.
Here's what i have tried so far -
public class BinaryTree {
static Node root;
public static void levelorder(Node<?> n) {
Queue<Node<?>> nodequeue = new LinkedList<Node<?>>();
if (n != null)
nodequeue.add(n);
while (!nodequeue.isEmpty()) {
Node<?> next = nodequeue.remove();
System.out.print(next.data + " ");
if (next.getLeft() != null) {
nodequeue.add(next.getLeft());
}
if (next.getRight() != null) {
nodequeue.add(next.getRight());
}
}
}
private static String[] breakString(String elements) {
int indexOfOpenBracket = elements.indexOf("(");
int indexOfLastBracket = elements.lastIndexOf(")");
String removedPString = elements.substring(indexOfOpenBracket + 1,
indexOfLastBracket);
String[] breakRemovedPString = removedPString.split(" ");
if (breakRemovedPString[1].contains("(")) {
add(breakRemovedPString[0], breakRemovedPString[1], breakRemovedPString[2]);
}
return breakRemovedPString;
}
static void add(String parent, String leftString, String rightString) {
Node<String> nodeToAdd = new Node<String>(parent);
if (root == null) {
root = nodeToAdd;
root.left = new Node<String>(leftString);
root.right = new Node<String>(rightString);
} else {
}
}
public static void main(final String[] args) {
String treeString = "(1 (2) (3))";
breakString(treeString);
levelorder(root);
System.out.println();
}
}
Please suggest some implementation for this problem.

This is a classical parsing problem. The simplest approach is probably recursive descent. Here is a grammar for the tree language:
T -> ( number T T )
| ( number )
| ()
To turn this into a parser, we can go through a formal transformation to LL(1) form and then code. I'll let you read up on that and show what results.
package treereader;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintStream;
import java.io.Reader;
enum Token { LPAREN, RPAREN, NUMBER, EOF, ERROR };
class Scanner {
final Reader in;
final char [] buf = new char[1];
final StringBuilder token = new StringBuilder();
private static final char EOF_MARK = Character.MIN_VALUE;
Scanner(Reader in) {
this.in = in;
read();
}
final void read() {
try {
if (in.read(buf) < 1) {
buf[0] = EOF_MARK;
}
} catch (IOException ex) {
System.err.println("i/o error");
buf[0] = EOF_MARK;
}
}
Token getNext() {
while (Character.isWhitespace(buf[0])) {
read();
}
if (Character.isDigit(buf[0])) {
token.setLength(0);
do {
token.append(buf[0]);
read();
} while (Character.isDigit(buf[0]));
return Token.NUMBER;
}
if (buf[0] == '(') {
read();
return Token.LPAREN;
}
if (buf[0] == ')') {
read();
return Token.RPAREN;
}
if (buf[0] == EOF_MARK) {
return Token.EOF;
}
return Token.ERROR;
}
String getString() {
return token.toString();
}
}
class Node {
public void print(PrintStream out) {
out.print("()");
}
}
class UnaryNode extends Node {
int val;
public UnaryNode(int val) {
this.val = val;
}
#Override
public void print(PrintStream out) {
out.print("(" + val + ")");
}
}
class BinaryNode extends Node {
int val;
Node left, right;
public BinaryNode(int val, Node left, Node right) {
this.val = val;
this.left = left;
this.right = right;
}
#Override
public void print(PrintStream out) {
out.print("(" + val + " ");
left.print(out);
out.print(' ');
right.print(out);
out.print(')');
}
}
class Parser {
final Scanner scanner;
Token lookAhead;
Parser(Reader in) {
scanner = new Scanner(in);
lookAhead = scanner.getNext();
}
void advance() {
lookAhead = scanner.getNext();
}
void match(Token token) throws IOException {
if (lookAhead == token) {
advance();
} else {
throw new IOException("Expected " + token + ", found " + lookAhead);
}
}
Node parse() throws IOException {
Node tree;
match(Token.LPAREN);
if (lookAhead == Token.NUMBER) {
int val = Integer.valueOf(scanner.getString());
advance();
if (lookAhead == Token.LPAREN) {
Node left = parse();
Node right = parse();
tree = new BinaryNode(val, left, right);
} else {
tree = new UnaryNode(val);
}
} else {
tree = new Node();
}
match(Token.RPAREN);
return tree;
}
}
public class TreeReader {
public static void main(String[] args) {
try {
Parser parser = new Parser(new BufferedReader(new FileReader(new File(args[0]))));
Node tree = parser.parse();
tree.print(System.out);
} catch (IOException ex) {
System.err.println(ex.getMessage());
}
}
}

Eclipse not running Java Code

Am really new to Java, started to study it on my own.... I downloaded netbeans and Eclipse and the two gave me the same result.. they don't run the code (stuck on running) neither let me debug it - Eclipse debugger and Netbeans - was not responding :? I don't whats wrong.. and I got no clue as I can't debug..
Here's my code: am tryin to check for palindrome:
package ClassQueue;
class Stack {
private Object[] Stack_Array = null;
public int top = 0;
public Stack(int size) {
top = 0;
Stack_Array = new Object[size];
}
public Stack() {
this(100);
}
protected void finalizer() {
Stack_Array = null;
}
final public boolean empty() {
return top == 0;
}
final public boolean full() {
return top == Stack_Array.length;
}
public void push(Object token) {
if (!full()) {
Stack_Array[top] = token;
top++;
}
}
public Object pop() {
Object Value_return = -999;
if (!empty()) {
Value_return = Stack_Array[top];
top--;
}
return Value_return;
}
}//end of Class_Stack
class Queue {
private Object[] Queue_Array = null;
private int Front = 0;
private int Rear = 0;
public Queue(int size) {
Front = Rear = 0;
Queue_Array = new Object[size];
}
public Queue() {
this(100);
}
protected void finalizer() {
Front = Rear = 0;
Queue_Array = null;
}
final public boolean empty() {
return Front == Rear;
}
final public boolean full() {
return Rear == Queue_Array.length;
}
public void queueAdd(Object token) {
if (!full()) {
Queue_Array[Rear] = token;
Rear++;
}
}
public Object queueDelete() {
Object Value_return = -999;
if (!empty()) {
Value_return = Queue_Array[Front];
Front++;
return Value_return;
}
return Value_return;
}
}//end of Class_Queue
public class ClassQueue {
public static void main(String[] args) {
int i = 0;
String Value_1 = "ABBA";
Stack Value_1_Stack = new Stack(Value_1.length());
Queue Value_1_Queue = new Queue(Value_1.length());
while (i < Value_1.length()) {
Value_1_Stack.push(Value_1.charAt(i));
Value_1_Queue.queueAdd(Value_1.charAt(i));
}
i = 0;
while (Value_1_Stack.pop() == Value_1_Queue.queueDelete()) {
i++;
}
if (i == Value_1.length()) {
System.out.println("Palindrome");
} else {
System.out.println("NOT");
}
}//end of main
}//end of ClassQueue

You've got an infinite loop here as i is never incremented:
while (i < Value_1.length()) {
Value_1_Stack.push(Value_1.charAt(i));
Value_1_Queue.queueAdd(Value_1.charAt(i));
}
Also don't exceed the length of the String Value_1:
while (i < Value_1.length() - 1) {
Value_1_Stack.push(Value_1.charAt(i));
Value_1_Queue.queueAdd(Value_1.charAt(i));
i++;
}
Aside: Use Java naming conventions for variable names.

You cannot create class with the name of package name.
To run your program
change the package name.
For ClassQueue create another ClassQueue.java file in same package.
To Debug program: Run>Debug
This will give you environment for debugging
Change view: Window>Show View>Debug

Java DFS implementation for n-puzzle, with hashmap

I'm writing program with several different algorithms for solving n-puzzle problem. I have problem with DFS algorithm, as it only finds solution for simplest combinations of depth 1 to 4, then it shows stack overflow error. Also, for depth 4 it shows solution of length 2147, which is obviously wrong. I ran out of ideas what is the problem.
I use HashMap to keep explored nodes and to retrace path. Here is my code for DFS:
public class DFS extends Path{
Node initial;
Node goal;
String order;
boolean isRandom = false;
ArrayList<Node> Visited = new ArrayList<Node>();
boolean goalFound=false;
public DFS(Node initial, String order, byte [][] goal_state){
this.initial=initial;
goal=new Node(goal_state);
this.order=order;
if(order.equals("Random"))isRandom=true;
Visited.add(initial);
path.put(this.initial, "");
runDFS(initial);
}
public void runDFS(Node current){
if(current.equals(goal))
{
goalFound=true;
System.out.println("Goal");
retracePath(current,true);
return;
}
if(!current.equals(goal) && goalFound==false)
{
Node child;
Moves m = new Moves(current);
if(isRandom)order=randomOrder("LRUD");
for (int i=0; i<4; i++)
{
String s = order.substring(i,i+1);
if(m.CanMove(s)==true)
{
child=m.move();
if(Visited.contains(child))
{
continue;
}
else
{
path.put(child,s);
Visited.add(child);
runDFS(child);
}
}
}
}
}
}
Node:
public class Node {
public byte[][] status;
private int pathcost;
public int getPathcost() {
return pathcost;
}
public void setPathcost(int pathcost) {
this.pathcost = pathcost;
}
public Node(byte[][] status)
{
this.status=new byte[status.length][status[0].length];
for(int i=0;i<status.length;i++){
for(int j=0;j<status[0].length;j++){
this.status[i][j]=status[i][j];
} }
}
#Override
public boolean equals(Object other)
{
if (!(other instanceof Node))
{
return false;
}
return Arrays.deepEquals(status, ((Node)other).status);
}
#Override
public int hashCode()
{
return Arrays.deepHashCode(status);
}
}
and Path:
public class Path {
public HashMap<Node,String> path;
public Path(){
path=new HashMap<Node, String>(100);
}
public void retracePath(Node nstate, boolean print){
String dir=path.get(nstate);
String textPath="";
int i=0;
while(!dir.equals("")){
textPath+=dir + ", ";
boolean changed=false;
if(dir.equals("L")) {dir="R"; changed=true;}
if(dir.equals("R") && changed==false) {dir="L";}
if(dir.equals("U")) {dir="D"; changed=true;}
if(dir.equals("D") && changed==false) {dir="U";}
Moves m=new Moves(nstate);
m.CanMove(dir);
nstate=new Node(m.move().status);
dir=path.get(nstate);
i++;
}
if(print==true) {textPath=textPath.substring(0,(textPath.length()-2));
System.out.println(i);
System.out.print(new StringBuffer(textPath).reverse().toString());}
}
public Node getParent(Node n){
String dir=path.get(n);
boolean changed=false;
if(dir.equals("L")) {dir="R"; changed=true;}
if(dir.equals("R") && changed==false) {dir="L";}
if(dir.equals("U")) {dir="D"; changed=true;}
if(dir.equals("D") && changed==false) {dir="U";}
Moves m=new Moves(n);
m.CanMove(dir);
n=new Node(m.move().status);
return n;
}
public String randomOrder(String order) {
ArrayList<Character> neworder = new ArrayList<Character>();
for(char c : order.toCharArray()) {
neworder.add(c);
}
Collections.shuffle(neworder);
StringBuilder newstring = new StringBuilder();
for(char c : neworder) {
newstring.append(c);
}
return newstring.toString();
}
}
If you have any ideas what is the problem and where is mistake I would be very thankful!