Develop Reference

PALIN- The next Palindrome - a SPOJ problem

I have opened an account for Ridit, one of 7-years-old students learning Java at SPOJ. The first task i gave to him was PALIN -The Next Palindrome. Here is the link to this problem- PALIN- The next Palindrome- SPOJAfter i explained it to him, he was able to solve it mostly except removing the leading zeros, which i did. Following is his solution of the problem -
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
// TODO Auto-generated method stub
try {
Scanner in = new Scanner(System.in);
int t = Integer.parseInt(in.nextLine());
String[] numbersInString = new String[t];
for (int i = 0; i <t; i++) {
String str = in.nextLine();
numbersInString[i] = removeLeadingZeros(str);
}
for (int i = 0 ; i<t; i++) {
int K = Integer.parseInt(numbersInString[i]);
int answer = findTheNextPalindrome(K);
System.out.println(answer);
}
}catch(Exception e) {
return;
}
}
static boolean isPalindrome(int x) {
String str = Integer.toString(x);
int length = str.length();
StringBuffer strBuff = new StringBuffer();
for(int i = length - 1;i>=0;i--) {
char ch = str.charAt(i);
strBuff.append(ch);
}
String str1 = strBuff.toString();
if(str.equals(str1)) {
return true;
}
return false;
}
static int findTheNextPalindrome(int K) {
for(int i = K+1;i<9999999; i++) {
if(isPalindrome(i) == true) {
return i;
}
}
return -1;
}
static String removeLeadingZeros(String str) {
String retString = str;
if(str.charAt(0) != '0') {
return retString;
}
return removeLeadingZeros(str.substring(1));
}
}
It is giving correct answer in Eclipse on his computer, but it is failing in SPOJ. If someone helps this little boy in his first submission, it will definitely make him very happy. I couldn't find any problem with this solution... Thank you in advance...

This might be helpful
import java.io.IOException;
import java.util.Scanner;
public class ThenNextPallindrom2 {
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
int t = 0;
Scanner sc = new Scanner(System.in);
if(sc.hasNextInt()) {
t = sc.nextInt();
}
sc.nextLine();
int[] arr, arr2;
while(t > 0) {
t--;
String s = sc.nextLine();
arr = getStringToNumArray(s);
if(all9(arr)) {
arr2 = new int[arr.length + 1];
arr2[0] = 1;
for(int i=0;i<arr.length;i++) {
arr2[i+1] = 0;
}
arr2[arr2.length -1] = 1;
arr = arr2;
} else{
int mid = arr.length/ 2;
int left = mid-1;
int right = arr.length % 2 == 1 ? mid + 1 : mid;
boolean left_small = false;
while(left >= 0 && arr[left] == arr[right]) {
left--;
right++;
}
if(left < 0 || arr[left] < arr[right]) left_small = true;
if(!left_small) {
while(left >= 0) {
arr[right++] = arr[left--];
}
} else {
mid = arr.length/ 2;
left = mid-1;
int carry = 1;
if(arr.length % 2 == 0) {
right = mid;
} else {
arr[mid] += carry;
carry = arr[mid]/10;
arr[mid] %= 10;
right = mid + 1;
}
while(left >= 0) {
arr[left] += carry;
carry = arr[left] / 10;
arr[left] %= 10;
arr[right++] = arr[left--];
}
}
}
printArray(arr);
}
}
public static boolean all9(int[] arr) {
for(int i=0;i<arr.length;i++) {
if(arr[i] != 9)return false;
}
return true;
}
public static void printArray(int[] arr) {
for(int i=0;i<arr.length;i++) {
System.out.print(arr[i]);
}
System.out.println();
}
public static int[] getStringToNumArray(String s) {
int[] arr = new int[s.length()];
for(int i=0; i<s.length();i++) {
arr[i] = Integer.parseInt(String.valueOf(s.charAt(i)));
}
return arr;
}
}

Java program using union-find + treemap too slow

I am solving this challenge: https://open.kattis.com/problems/virtualfriends
My solution seems to be working but kattis's test cases are running too slowly so I was wondering how I can improve code efficiency. I am using a custom made union-find structure to do this, storing "friends" into a treemap to reference.
import java.util.*;
public class virtualfriends {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int testcases = scan.nextInt();
scan.nextLine();
for (int i= 0; i < testcases; i++) {
int numFriendships = scan.nextInt();
scan.nextLine();
TreeMap<String , Integer> map = new TreeMap<String , Integer>();
int cnt = 0;
UF unionFind = new UF(50000);
for (int j = 0; j < numFriendships; j++)
{
String p1 = scan.next();
String p2 = scan.next();
if (!map.containsKey(p1)) map.put(p1, cnt++);
if (!map.containsKey(p2)) map.put(p2, cnt++);
unionFind.unify(map.get(p1), map.get(p2));
System.out.printf("%d\n", unionFind.getSetSize(map.get(p2)));
}
}
}
static class UF{
private int[] id, setSize;
private int numSets;
public UF(int size) {
id = new int[size] ;
setSize = new int[size];
numSets = size;
for(int i = 0 ; i < size ; ++i) {
id[i] = i;
setSize[i] = 1;
}
}
int find(int i )
{
int root = i;
while (root != id[root]) {
root = id[root];
}
while (i != root) {
int newp = id[i];
id[i] = root;
i = newp;
}
return root;
}
boolean isConnected(int i , int j) {
return find(i) == find(j);
}
int getNumSets() {
return numSets;
}
int getSetSize(int i) {
return setSize[find(i)];
}
boolean isSameSet(int i, int j) {
return find(i) == find(j);
}
void unify(int i, int j)
{
int root1 = find(i);
int root2 = find(j);
if (root1 == root2) return;
if (setSize[root1] < setSize[root2])
{
setSize[root2] += setSize[root1];
id[root1] = root2;
} else {
setSize[root1] += setSize[root2];
id[root2] = root1;
}
numSets--;
}
}
}

Combinations redundant in java programme

I want to print every possible combinations by using given letters without change letter orders so i wrote this code but it will print every line again and again what is the problem
public class Solutions {
public static void main(String[] args) {
// Scanner scanner = new Scanner(System.in);
c = "l u k".split(" ");
Solutions solutions = new Solutions();
solutions.combi(0);
System.out.println("Number of combi = " + count);
System.out.print(max);
}
static String[] c;
static int count = 0;
static int max = 0;
public void combi(int start) {
int j;
if (start != 0) {
String str = "";
for (int i = 0; i < start; i++) {
// System.out.print(c[i]);
str += c[i];
}
// System.out.println();
count++;
}
for (j = start; j < c.length; j++) {
combi(start + 1);
}
}
}

public void combi(int start) {
int j;
if (start != 0) {
for (int i = 0; i < start; i++) {
System.out.print(c[i]);
}
System.out.println();
count++;
} else {
for (j = start+1; j <= c.length; j++) {
combi(j);
}
}
}

illegal start of expression in java while declaring private variables in public class

import java.util.InputMismatchException;
import java.util.Scanner;
import java.util.Stack;
public class TSPNearestNeighbour {
{
private final Stack<Integer> stack;
private int numberOfNodes;
public TSPNearestNeighbour()
{
stack = new Stack<Integer>();
}
public void tsp(int adjacencyMatrix[][])
{
numberOfNodes = adjacencyMatrix[1].length - 1;
int[] visited = new int[numberOfNodes + 1];
visited[1] = 1;
stack.push(1);
int element, dst = 0, i,cost=0;
int min = Integer.MAX_VALUE;
boolean minFlag = false;
System.out.print(1 + "\t");
while (!stack.isEmpty())
{
element = stack.peek();
i = 1;
min = Integer.MAX_VALUE;
while (i <= numberOfNodes)
{
if (adjacencyMatrix[element][i] > 1 && visited[i] == 0)
{
if (min > adjacencyMatrix[element][i])
{
min = adjacencyMatrix[element][i];
cost=cost+adjacencyMatrix[element][i];
dst = i;
minFlag = true;
}
}
i++;
}
if (minFlag)
{
visited[dst] = 1;
stack.push(dst);
System.out.print( dst + "\t");
minFlag = false;
continue;
}
stack.pop();
}
System.out.println("total cost" +cost);
}
public static void main(String args[])
{
int number_of_nodes;
Scanner scanner = null;
try
{
System.out.println("Enter the number of nodes in the graph");
scanner = new Scanner(System.in);
number_of_nodes = scanner.nextInt();
int adjacency_matrix[][] = new int[number_of_nodes + 1][number_of_nodes + 1];
System.out.println("Enter the adjacency matrix");
for (int i = 1; i <= number_of_nodes; i++)
{
for (int j = 1; j <= number_of_nodes; j++)
{
adjacency_matrix[i][j] = scanner.nextInt();
}
}
for (int i = 1; i <= number_of_nodes; i++)
{
for (int j = 1; j <= number_of_nodes; j++)
{
if (adjacency_matrix[i][j] == 1 && adjacency_matrix[j][i] == 0)
{
adjacency_matrix[j][i] = 1;
}
}
}
System.out.println("the citys are visited as follows");
TSPNearestNeighbour tspNearestNeighbour = new TSPNearestNeighbour();
tspNearestNeighbour.tsp(adjacency_matrix);
} catch (InputMismatchException inputMismatch)
{
System.out.println("Wrong Input format");
}
scanner.close();
}
}
> illegal start of expression in the line:
> **private final Stack<Integer> stack;**

You have 2 open braces
public class TSPNearestNeighbour { {
remove one and may be you get your code compiled

Java Implementation, Priority Queue

I have a hard time to figure out one error after assigning
int evaluationNode = getMinDistances();
settled.add(evaluationNode);
checkNeighbours(evaluationNode);
The error show type mismatch: connot convert from Node to int. I am appreciated if anyone can help me this. Below is a complete code.
import java.util.HashSet;
import java.util.InputMismatchException;
import java.util.PriorityQueue;
import java.util.Scanner;
import java.util.Set;
import java.util.Comparator;
public class DijkstraPriorityQueue
{
private int distances[];
private Set<Integer> settled;
private PriorityQueue<Node> priorityQueue;
private int number_of_nodes;
private int adjacencyMatrix[][];
public DijkstraPriorityQueue(int number_of_nodes)
{
this.number_of_nodes = number_of_nodes;
distances = new int[number_of_nodes + 1];
settled = new HashSet<Integer>();
priorityQueue = new PriorityQueue<Node>(number_of_nodes,new Node());
adjacencyMatrix = new int[number_of_nodes + 1][number_of_nodes + 1];
}
public void dijkstra_algorithm(int adjacency_matrix[][], int source)
{
int evaluationNode;
for (int i = 1; i <= number_of_nodes; i++)
for (int j = 1; j <= number_of_nodes; j++)
adjacencyMatrix[i][j] = adjacency_matrix[i][j];
for (int i = 1; i <= number_of_nodes; i++)
{
distances[i] = Integer.MAX_VALUE;
}
priorityQueue.add(new Node(source, 0));
distances[source] = 0;
while (!priorityQueue.isEmpty())
{
evaluationNode = getMinDistances();
settled.add(evaluationNode);
evaluateNeighbours(evaluationNode);
}
}
private int getMinDistances()
{
int node = priorityQueue.remove();
return node;
}
private void checkNeighbours(int evaluationNode)
{
int edgeDistance = -1;
int newDistance = -1;
for (int destinationNode = 1; destinationNode <= number_of_nodes; destinationNode++)
{
if (!settled.contains(destinationNode))
{
if (adjacencyMatrix[evaluationNode][destinationNode] != Integer.MAX_VALUE)
{
edgeDistance = adjacencyMatrix[evaluationNode][destinationNode];
newDistance = distances[evaluationNode] + edgeDistance;
if (newDistance < distances[destinationNode])
{
distances[destinationNode] = newDistance;
}
priorityQueue.add(new Node(destinationNode,distances[destinationNode]));
}
}
}
}
public static void main(String[] args)
{
int adjacency_matrix[][];
int number_of_vertices;
int source = 0;
Scanner scan = new Scanner(System.in);
try
{
System.out.println("Enter the number of vertices");
number_of_vertices = scan.nextInt();
adjacency_matrix = new int[number_of_vertices + 1][number_of_vertices + 1];
System.out.println("Enter the Weighted Matrix for the graph");
for (int i = 1; i <= number_of_vertices; i++)
{
for (int j = 1; j <= number_of_vertices; j++)
{
adjacency_matrix[i][j] = scan.nextInt();
if (i == j)
{
adjacency_matrix[i][j] = 0;
continue;
}
if (adjacency_matrix[i][j] == 0)
{
adjacency_matrix[i][j] = Integer.MAX_VALUE;
}
}
}
System.out.println("Enter the source ");
source = scan.nextInt();
DijkstraPriorityQueue dijkstrasPriorityQueue = new DijkstraPriorityQueue(number_of_vertices);
dijkstrasPriorityQueue.dijkstra_algorithm(adjacency_matrix, source);
System.out.println("The Shorted Path to all nodes are ");
for (int i = 1; i <= dijkstrasPriorityQueue.distances.length - 1; i++)
{
System.out.println(source + " to " + i + " is " + dijkstrasPriorityQueue.distances[i]);
}
} catch (InputMismatchException inputMismatch)
{
System.out.println("Wrong Input Format");
}
scan.close();
}
}
class Node implements Comparator<Node>
{
public int node;
public int cost;
public Node()
{
}
public Node(int node, int cost)
{
this.node = node;
this.cost = cost;
}
#Override
public int compare(Node node1, Node node2)
{
if (node1.cost < node2.cost)
return -1;
if (node1.cost > node2.cost)
return 1;
return 0;
}
}

In the getMinDistances method you are calling
int node = priorityQueue.remove();
But the priority queue contains Node objects, and not int values.
Maybe you wanted something like
private int getMinDistances()
{
Node node = priorityQueue.remove();
return node.getDistance();
}
but this is something that can not be answered by the debugging cloud (aka stackoverflow).

In order to use the PriorityQueue, you have to implement MinPQ extending the PriorityQueue and you'll also need a Comparator between nodes that returns the Node with a minimum distance in the MinPQ.
Take a look here for more details.