Develop Reference

How to print only distinct integer values once even though they are repeated multiple times

I am trying to print only distinct integer values once even though they are repeated multiple times in an array with the introduced order. Firstly, I need to take array size from user but I cannot determine how to initialize that variable.Can I use n -inclueded in the code- as an array size variable? When I compiled I doesn't print anything. Where are my mistakes, and how to deal with them? Any idea?
public static void uniqueNumbers(int arr[], int n)
{
for (int i=0; i<n; i++)
{
for (int j =0; j<i;j++)
{
if (arr [i]==arr[j])
break;
if (i==j)
System.out.print(arr[i] + " ");
}
}
}
public static void main(String[] args) {
Scanner sc =new Scanner(System.in);
int n =sc.nextInt();
int arr [] = new int [n];
uniqueNumbers(arr,n);
}
}

You need to fill the array,that is, you need to take input for the array elements.
public static void main(String[] args) {
Scanner sc =new Scanner(System.in);
int n =sc.nextInt();
int arr [] = new int [n];
//Add the following lines.
for (int i = 0; i < n; i++) {
arr[i] = sc.nextInt();
}
uniqueNumbers(arr,n);
}
Print the array and try your logic again.

you need to first request for the size of the array as shown below:
public static void main (String[] args)
{
Scanner scan = new Scanner(System.in);
System.out.println("Enter array size");
int n =scan.nextInt();
// declaring and creating array objects
int[] arr = new int[n];
// displaying default values
System.out.println("Default values of array:");
for (int i=0; i < arr.length; i++) {
System.out.print(arr[i]+"\t");
}
// initializing array
System.out.println("\n\n***Initializing Array***");
System.out.println("Enter "+ arr.length
+ " integer values:");
for(int i=0; i < arr.length; i++) {
// read input
arr[i] = scan.nextInt();
}
uniqueNumbers(arr, n);
}

public static void uniqueNumbers(int[] arr, int n) {
int slow = 1;
for (int fast = 1; fast < n; fast++) {
if (arr[fast] != arr[slow - 1]) {
arr[slow++] = arr[fast];
}
}
arr = Arrays.copyOf(arr, slow);
for (int i = 0; i < arr.length; i++) {
System.out.println(arr[i]);
}
}

Storing output of a nested loop as new array - Java

I need to find the largest prime number of a given array when adding two numbers in an array,so I decided to add all possible sums first and displayed it. Now I want to take those output elements to a new array.Please help me solve this problem.
import java.util.Scanner;
public class main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int noOfElem = scanner.nextInt();
int[] array = new int[noOfElem];
int[][] newArray = new int[5][4];
int i=0;
while(scanner.hasNextInt()){
array[i] = scanner.nextInt();
i++;
if(i == noOfElem){
break;
}
}
for (int a = 0; a < array.length; a++)
{
for (int b = a+1; b < array.length; b++) {
int m = array[a] + array[b];
newArray[a][b] =
}
}
}
}

Not quite sure what the problem is here, just do
newArray[a][b] = m;
This stores all sums of all 'a's and 'b's such that newArray[a][b] is the sum of array[a] + array[b]

Inputting adjacency matrix from a file

I am attempting to input the following file into my program in the form of an adjacency matrix.
16
-1,1075,716,792,1425,1369,740,802,531,383,811,2211,661,870,999,772
1075,-1,1015,1770,2403,1662,870,1858,941,1426,1437,3026,1486,211,1463,314
716,1015,-1,928,1483,646,390,1085,185,749,530,2034,1377,821,471,772
792,1770,928,-1,633,1089,1111,246,908,409,495,1447,1317,1565,672,1470
1425,2403,1483,633,-1,9999,1630,752,1432,9999,931,814,1938,2198,1016,2103
1369,1662,646,1089,9999,-1,820,1335,832,9999,605,1839,2030,1468,421,1419
740,870,390,1111,1630,820,-1,1224,360,965,690,2197,1480,750,630,705
802,1858,1085,246,752,1335,1224,-1,1021,442,737,1566,1190,1653,918,1558
531,941,185,908,1432,832,360,1021,-1,685,496,2088,1192,736,616,656
383,1426,749,409,9999,9999,965,442,685,-1,738,1858,1938,1221,926,1126
811,1437,530,495,931,605,690,737,496,738,-1,1631,1472,1232,188,1152
2211,3026,2034,1447,814,1839,2197,1566,2088,1858,1631,-1,2752,2824,1563,2744
661,1486,1377,1317,1938,2030,1480,1190,1192,1938,1472,2752,-1,1281,1660,1183
870,211,821,1565,2198,1468,750,1653,736,1221,1232,2824,1281,-1,1269,109
999,1463,471,672,1016,421,630,918,616,926,188,1563,1660,1269,-1,1220
772,314,772,1470,2103,1419,705,1558,656,1126,1152,2744,1183,109,1220,-1
However, I think I have something wrong with my logic or I'm not using the Scanner correctly. This is my code:
public class Tour
{
public static final int N = 16;
public static final int INF = Integer.MAX_VALUE;
public static void printGrid(int[][] adjMat)
{
for(int i = 0; i < 16; i++)
{
for(int j = 0; j < 16; j++)
{
if(adjMat[i][j] == INF)
System.out.printf("%5s", 0);
else
System.out.printf("%5d", adjMat[i][j]);
}
System.out.println();
}
}
public static void main(String[] args) throws IOException
{
File file = new File("american_tour.dat");
Scanner scanner = new Scanner(file);
int[][] adjMat = new int[N][N];
for(int i = 0, n = scanner.nextInt(); i < n; i++)
for(int j = 0; j < n; j++)
adjMat[i][j] = n;
scanner.close();
printGrid(adjMat);
}
}
Could someone show me how to properly input the data from the file into an adjacency matrix?

Improving Mouad's answer, using the scanner's built in support for custom delimiters:
Scanner scanner = new Scanner(file);
scanner.useDelimiter("[\\s,]+");
int N = scanner.nextInt();
int[][] adjMat = new int[N][N];
for(int i=0; i < N; i++) {
for (int j=0; j < N; j++) {
adjMat[i][j] = scanner.nextInt();
}
}
scanner.close();

As your data does not respect a specific pattern for delimiters, try this instead :
public static void main(String[] args) throws FileNotFoundException {
File file = new File("E:\\american_tour.dat");
Scanner scanner = new Scanner(file);
//N in the example equals 16
int N = scanner.nextInt();
//skip the first line
scanner.nextLine();
int[][] adjMat = new int[N][N];
for(int i = 0; i < N; i++){
String[] lines = scanner.nextLine().split(",");
for (int j=0; j<lines.length; j++) {
adjMat[i][j] = Integer.parseInt(lines[j]);
}
}
scanner.close();
}

Although not exceed index, I get error by the index

My question is
( - Write the following method that merges two sorted lists
into a new sorted list. Write a test program that prompts the user to enter two sorted lists and displays the merged list. Here is a sample run. Note that the first number in the input indicates the number of the elements in the list. - )
When I run this code, Eclipse give error.
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 3
at single_dimension_all_arrays.Merge_two_sorted_lists.getNumber(Merge_two_sorted_lists.java:60)
at single_dimension_all_arrays.Merge_two_sorted_lists.main(Merge_two_sorted_lists.java:77)
I can't understand why give the error. I can't exceed index.
private static void sort(int [] list3)
{
int temp=0;
for (int i = 0; i < list3.length; i++)
{
for (int j = 0; j < list3.length; j++)
{
if(list3[i]<list3[j])
{
temp=list3[i];
list3[i]=list3[j];
list3[j]=temp;
}
}
}
for (int i = 0; i < list3.length; i++)
{
System.out.println(list3[i]);
}
}
private static void getNumber(int [] list1,int [] list2)
{
Scanner scan = new Scanner(System.in);
int [] list3 = new int[list1.length+list2.length];
for (int i = 1; i < list1.length; i++)
{
System.out.println("Please, enter the number");
list1[i] = scan.nextInt();
}
for (int i = 1; i < list2.length; i++)
{
System.out.println("Please,enter the number");
list2[i]= scan.nextInt();
}
for (int i = 0; i <= list3.length; i++)
{
if(i<list1.length)
{
list3[i]=list1[i];
}
else if(i>list1.length)
{
list3[i] = list2[i];
}
}
sort(list3);
}
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
System.out.println("Please,enter the length of list1");
int l1 = scan.nextInt();
System.out.println("Please, enter the length of list2");
int l2 = scan.nextInt();
int [] list1 = new int[l1];
int [] list2 = new int[l2];
list1[0]=l1;
list2[0]=l2;
getNumber(list1,list2);
}
}
Thanks..:)

Although not exceed index...
Yes you do:
for (int i = 0; i <= list3.length; i++)
// ----------------^
The valid range of indexes is 0 to length - 1, so that should be < as it is in several other parts of your code.
Side note: You're also skipping the first element in arrays in a few places:
for (int i = 1; i < list1.length; i++)
// ----------^

ways to speed up the Full Counting Sort

I encountered a question on hackerrank.
https://www.hackerrank.com/challenges/countingsort4
My first attempt passed all the test cases except the last one, due to timeout.
After failed to come up with a more efficient algorithm, I improved the code by using StringBuilder instead of concatenating Strings directly. This brought the running time from more than 5 sec to 3.5 sec.
My question is that is there any other way that I can improve the running time?
Thanks.
The following is my code.
public class Solution {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int N = scanner.nextInt();
scanner.nextLine();
int[] oriNum = new int[N];
String[] oriStr = new String[N];
int[] count = new int[100];
int[] indices = new int[100];
int[] output = new int[N];
// save the originals and the count array
for (int i = 0; i < N; i++) {
oriNum[i] = scanner.nextInt();
oriStr[i] = scanner.nextLine().trim();
count[oriNum[i]]++;
}
// accumulate the count array
indices[0] = 0;
for (int i = 1; i < 100; i++) {
indices[i] = indices[i-1] + count[i-1];
}
// output order
for (int i = 0; i < N; i++) {
int num = oriNum[i];
output[indices[num]++] = i;
}
int bar = N/2;
StringBuilder sb = new StringBuilder();
for (int i = 0; i < N; i++) {
int index = output[i];
if (index < bar)
sb.append("- ");
else
sb.append(oriStr[index]+ " ");
}
System.out.println(sb.toString());
}
}

You should try a plain buffered reader instead of Scanner. Scanner is surprisingly slow and I have participated in programming competitions where Scanner was the sole reason for "time limit exceeded".

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
public class Solution
{
public static void main(String[] args)throws Exception
{
BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
int n=Integer.parseInt(in.readLine());
int[] c=new int[100];
String[][] dt=new String[100][10300];
for(int i=0;i<n;i++)
{
String[] str=in.readLine().split(" ");
int val=Integer.parseInt(str[0]);
if(i<n/2)
dt[val][c[val]]="-";
else
dt[val][c[val]]=str[1];
c[val]++;
}
StringBuilder sb=new StringBuilder("");
for(int i=0;i<100;i++)
if(i<n)
for(int k=0;k<c[i];k++)
if(dt[i][k]!=null)
sb.append(dt[i][k]+" ");
else break;
System.out.println(sb.toString());
}
}

This was my approach to problem. (it is in c++).
void counting_sort(vector<int> &arr, int size, vector<vector<string> > foo, vector<int> first_half)
{
int max = *max_element(arr.begin(), arr.end());
int min = *min_element(arr.begin(), arr.end());
int range = max - min + 1;
int count[range] = {0};
// counting frequency of numbers in array
for (int i = 0; i < size; i++)
{
count[arr[i] - min]++;
}
// calculating cumulative sum
for (int i = 1; i < range; i++)
{
count[i] += count[i - 1];
}
vector<vector<string> > output(size);
// making the new sorted array
for (int i = size - 1; i >= 0; i--) // traversing from backward for stability
{
output[count[arr[i]-min] - 1] = foo[i];
count[arr[i]-min]--;
}
// copying the sorted array in original array
int j=0;
for (int i = 0; i < size; i++)
{
if(stoi(output[i][0]) == first_half[j])
{
cout << "- ";
j++;
}
else
{
cout << output[i][1] << ' ';
}
}
}
// Complete the countSort function below.
void countSort(vector<vector<string>> arr) {
vector<int> num;
vector<int> first_half;
for(int i=0; (unsigned)i<arr.size(); i++)
{
num.push_back(stoi(arr[i][0]));
if(i < ((unsigned)arr.size()/2))
{
first_half.push_back(stoi(arr[i][0]));
}
}
sort(first_half.begin(), first_half.end());
counting_sort(num, num.size(), arr, first_half);
}