We Keep Coding

How to use the insertColumn(int j, vector column)

I just need to insert rows and columns of zeros in a matrix
tried to get exmples from web searches
ArrayList<double [][]> al = new ArrayList<>();
for (int i1= 0; i1<=i; i1++)
al.add(k);
System.out.println(al.size());
double[][] firstMatrix = al.get(i);
double [][] matrix1 = al.get(i);
double [][] matrix2 = al.get(i);
Matrix Matrix1 = new Matrix (matrix1);
Matrix1.show();
System.out.println();
Matrix1.insertColumn(0,0.0, 0.0, 0.0, 0.0);
Matrix1.show();
System.out.println();

Your question boils down to adding a new column/row to a Java array. This is not possible per se, because your array has an exact memory area allocated to it and you would need a larger memory area for the resulting array, so, the solution is to create a new array and solve the problem that way:
Adding a row
double[][] addRow(double[][] input, int where) {
double[][] output = new double[input.length + 1][input[0].length];
for (int rIndex = 0; rIndex < output.length; rIndex++) {
for (int cIndex = 0; cIndex < output[0].length; cIndex++) {
if (rIndex < where) output[rIndex][cIndex] = input[rIndex][cIndex];
else if (rIndex == where) output[rIndex][cIndex] = 0;
else output[rIndex][cIndex] = input[rIndex - 1][cIndex];
}
}
return output;
}
Adding a column
double[][] addColumn(double [][]input, int where) {
double[][] output = new double[input.length][input[0].length + 1];
for (int rIndex = 0; rIndex < output.length; rIndex++) {
for (int cIndex = 0; cIndex < output[0].length; cIndex++) {
if (cIndex < where) output[rIndex][cIndex] = input[rIndex][cIndex];
else if (cIndex == where) output[rIndex][cIndex] = 0;
else output[rIndex][cIndex] = input[rIndex][cIndex - 1];
}
}
return output;
}
and make sure you assign the result of these methods to whatever variable/member you have used as the data source.

Extract numbers from a array and divide them (positives and negatives) into separate arrays

I want to extract numbers from an array and divide them into positives and negatives into separate arrays. Why does my Java code does not work?
How to make it work?
int pole[] = new int[20];
int pock = 0;
int pocz = 0;
int pocn = 0;
for (int i = 0; i < pole.length; i++) {
pole[i] = (int)(-10+Math.random()*21);
}
for (int i = 0; i < 10; i++) {
if(pole[i]>0)pock++;
else if(pole[i]<0) pocz++;
else pocn++;
}
int pklad[] = new int[pock];
int pzap[] = new int [pocz];
int n[] = new int [pocn];
int j = 0;
for (int i = 0; i < pole.length; i++) {
if(pole[i]>0){
pklad[j] = pole[i];
}if(pole[i]<0){
pzap[j] = pole[i];
}else n[j]=pole[i];
j++;
}
System.out.print("All positives: ");
for (int i = 0; i < pock; i++) {
System.out.print(pklad[i]+",");
}
System.out.println();
System.out.print("All negatives: ");
for (int i = 0; i < pocz; i++) {
System.out.println(pzap[i]);
}
System.out.print("Zeros: ");
for (int i = 0; i < pocn; i++) {
System.out.println(n[i]);
}
Edit: This throws an exception: (thanks, BRjava)
ArrayIndexOutOfBoundsException, line 36

Use the ArrayList it is better than normal arrays.
public static void main(String[] args) {
ArrayList<Double> yourNumbers = new ArrayList<Double>();
yourNumbers.add(54.2); //add some number to our array
yourNumbers.add(-67.7);
ArrayList<Double> positive = new ArrayList<>();
ArrayList<Double> negative = new ArrayList<>();
for(Double currentNumber : yourNumbers) {
if(currentNumber >= 0) {
positive.add(currentNumber);
}else if(currentNumber <0) {
negative.add(currentNumber);
}
}
//print all positive numbers
for(Double currentDouble : positive) {
System.out.println("Positive: "+currentDouble);
}
//print all negative numbers
for(Double currentDouble : negative) {
System.out.println("Negative: "+currentDouble);
}
}

The problem is that you have three arrays, pklad[], pzap[], and n[], but you try using a single index j to write to all three. This is what is causing your ArrayIndexOutOfBoundsException: as soon as j goes past the limit of the shorter of the arrays, an attempted write causes the exception.
You need three separate indexes, say, jpos, jneg, and jn, all initialized to zero before the loop. Each index needs to be incremented individually when you write to its corresponding array:
for (int i = 0; i < pole.length; i++) {
if (pole[i] > 0) {
pklad[jpos++] = pole[i];
} else if (pole[i] < 0) {
pzap[jneg++] = pole[i];
} else {
n[jn++]=pole[i];
}
}

code does not work with arrays (multiple arrays in arraylist)

hi I'm having a little problem with arrays.
here's the code:
int frame_size = 410;
int frame_shift = 320;
ArrayList<double[]> frames = new ArrayList<double[]>();
for (int i = 0; i + frame_size < inbuf.length; i = i + frame_shift) {
double[] frame = new double[frame_size];
System.arraycopy(inbuf, i, frame, 0, frame_size);
frames.add(frame);
}
here I share a large array into several small, and add them to arraylist
I need to get more of ArrayList arrays and pass them to the function, and then accept the answer and assemble arrays processed one:
int[] Cover = new int[frames.size() * nParam];
for (int i = 0; i < frames.size(); i++) {
double[] finMc = Gos.getVek(frames.get(i));
for (int c = 0; c < finMc.length; c++) {
int mc = (int) finMc[c];
for (int m = 0; m < Cover.length; m++) {
Cover[m] = mc;
}
}
}
all this code does not work (
all elements of the array are zero Cover.
Сover[0] = 0
Cover[1] = 0
Cover[2] = 0
...
help solve the problem, please!)
thank you in advance)
Update
int frame_size = 410;
int frame_shift = 320;
ArrayList<double[]> frames = new ArrayList<double[]>();
for (int i = 0; i + frame_size < inbuf.length; i = i + frame_shift) {
double[] frame = new double[frame_size];
System.arraycopy(inbuf, i, frame, 0, frame_size);
frames.add(frame);
}
int[] Cover = new int[frames.size() * nParam];
for (int i = 0; i < frames.size(); i++) {
double[] finMc = Gos.getVek(frames.get(i));
for (int c = 0; c < finMc.length; c++) {
int mc = (int) finMc[c];
Cover[i * frames.size() + c] = (int) finMc[c];
}
}
Code^ not work(
UPDATE 2
double[] inbuf = new double[Size];
inbuf = toDoubleArray(Gos.data);
inbuf[2] = 10;
inbuf[4] = 14;
toDoubleArray
public static double[] toDoubleArray(byte[] byteArray) {
int times = Double.SIZE / Byte.SIZE;
double[] doubles = new double[byteArray.length / times];
for (int i = 0; i < doubles.length; i++) {
doubles[i] = ByteBuffer.wrap(byteArray, i * times, times)
.getDouble();
}
return doubles;
}
Code not work:
int frame_size = 410;
int frame_shift = 320;
ArrayList<double[]> frames = new ArrayList<double[]>();
for (int i = 0; i + frame_size < inbuf.length; i = i + frame_shift) {
double[] frame = new double[frame_size];
System.arraycopy(inbuf, i, frame, 0, frame_size);
frames.add(frame);
}
double[] Cover = new double[frames.size() * nParam];
for (int i = 0; i < frames.size(); i++) {
double[] finMc = Gos.getVek(frames.get(i));
for (int c = 0; c < finMc.length; c++) {
Cover[i * frames.size() + c] = finMc[c];
}
}

A couple of thoughts spring to mind immediately:
1)
for (int m = 0; m < Cover.length; m++) {
Cover[m] = mc;
}
This block starts m over at 0 every time through the loop. This means you're always writing over the same portion of the Cover array. So effectively, it's only the last frame's data that's stored. You probably meant
for(int m = i * frames.size(); m < (i+1)*frames.size(); i++) {
Cover[m] = mc;
}
But this raises a further issue -- you're writing the same value (mc) into the entire area allocated for a whole frame of data. You probably want to merge this loop with the previous loop so that this doesn't happen.
for (int c = 0; c < finMc.length; c++) {
Cover[i * frames.size() + c] = (int)finMc[c];
}
2) int mc = (int) finMc[c];
That line casts the value to an int which truncates the value stored at finMc[c]. If finMc[c] is between 0 and 1 this will yield 0 when the data is copied and casted. This is compounded by the previous issue which ensures that only the last frame's data ever gets copied. This is simply solved by removing the cast and declaring Cover as an array of doubles instead of ints.
So in sum, the code might work a bit better if it's written this way:
double[] Cover = new double[frames.size() * nParam];
for (int i = 0; i < frames.size(); i++) {
double[] finMc = Gos.getVek(frames.get(i));
for (int c = 0; c < finMc.length; c++) {
Cover[i * frames.size() + c] = finMc[c];
}
}

Merge Sort - Sorting String Array with Int Array

For this project, I'm given an array of strings and an array of ints. int[1] is the ranking for string[1]. I need to sort the int array in order from 1 to n using mergesort, which I've done below. But I also need to switch the positions of the string array when the int array gets moved so they are both sorted, if that makes sense? I can't figure out what's wrong with my coding or even if my idea will actually work, but I keep getting an array index out of bounds error on stringSorted[k] = stringRight[j] and I can't figure out if there's a way to fix this. Essentially, when an int was added to the sortedInt array, I also added that element to the sorted String array. Thank you for any help, and let me know if something doesn't make sense
private static int sortAndCount(int intToSort[]){
int inversionsLeft;
int inversionsRight;
int inversionsMerged;
if(intToSort.length == 1){
return 0;
}
int m = intToSort.length/2;
int[] intLeft = new int[m];
stringLeft = new String[m];
int[] intRight = new int[intToSort.length-m];
stringRight = new String[intToSort.length-m];
for (int i=0; i < m; i++){
intLeft[i] = intToSort[i];
stringLeft[i] = stringToSort[i];
}
for (int i = 0;i < intRight.length; i++){
intRight[i] = intToSort[m+i];
stringRight[i] = stringToSort[m+i];
}
inversionsLeft = sortAndCount(intLeft);
inversionsRight = sortAndCount(intRight);
intSorted = new int[intToSort.length];
stringSorted = new String[stringToSort.length];
inversionsMerged = mergeAndCount(intLeft, intRight);
return(inversionsLeft + inversionsRight + inversionsMerged);
}
private static int mergeAndCount(int[] intLeft, int[] intRight){
int count = 0;
int i = 0;
int j = 0;
int k = 0;
while(i < intLeft.length && j < intRight.length){
if(intLeft[i] < intRight[j]){
intSorted[k] = intLeft[i];
stringSorted[k] = stringLeft[i];
i++;
}
else{
intSorted[k] = intRight[j];
stringSorted[k] = stringRight[j];
count += intLeft.length - i + 1;
j++;
}
k++;
}
while (i < intLeft.length)
{
intSorted[k] = intLeft[i];
stringSorted[k] = stringLeft[i];
k++;
i++;
}
while (j < intRight.length)
{
intSorted[k] = intRight[j];
stringSorted[k] = stringRight[j];
j++;
k++;
}
return count;
}
}

int[] intLeft = new int[m];
stringLeft = new String[m];
int[] intRight = new int[intToSort.length-m];
stringRight = new String[intToSort.length-m];
You'll notice here that for the int arrays you are creating new variables, for the string you are replacing the outer. This is making your string arrays smaller with each recursive call whereas your int arrays are passed to each method.
By the time you get to calling mergeAndCount, stringLeft and stringRight are very small whereas the appropriately sized intLeft and intRight are passed as arguments.

Java Sudoku Generator(easiest solution)

In my last question seen here: Sudoku - Region testing I asked how to check the 3x3 regions and someone was able to give me a satisfactory answer (although it involved a LOT of tinkering to get it working how I wanted to, since they didn't mention what the class table_t was.)
I finished the project and was able to create a sudoku generator, but it feels like it's contrived. And I feel like I've somehow overcomplicated things by taking a very brute-force approach to generating the puzzles.
Essentially my goal is to create a 9x9 grid with 9- 3x3 regions. Each row / col / region must use the numbers 1-9 only once.
The way that I went about solving this was by using a 2-dimensional array to place numbers at random, 3 rows at a time. Once the 3 rows were done it would check the 3 rows, and 3 regions and each vertical col up to the 3rd position. As it iterated through it would do the same until the array was filled, but due to the fact that I was filling with rand, and checking each row / column / region multiple times it felt very inefficient.
Is there an "easier" way to go about doing this with any type of data construct aside from a 2d array? Is there an easier way to check each 3x3 region that might coincide with checking either vert or horizontal better? From a standpoint of computation I can't see too many ways to do it more efficiently without swelling the size of the code dramatically.

I built a sudoku game a while ago and used the dancing links algorithm by Donald Knuth to generate the puzzles. I found these sites very helpful in learning and implementing the algorithm
http://en.wikipedia.org/wiki/Dancing_Links
http://cgi.cse.unsw.edu.au/~xche635/dlx_sodoku/
http://garethrees.org/2007/06/10/zendoku-generation/

import java.util.Random;
import java.util.Scanner;
public class sudoku {
/**
* #antony
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
int p = 1;
Random r = new Random();
int i1=r.nextInt(8);
int firstval = i1;
while (p == 1) {
int x = firstval, v = 1;
int a[][] = new int[9][9];
int b[][] = new int[9][9];
for (int i = 0; i < 9; i++) {
for (int j = 0; j < 9; j++) {
if ((x + j + v) <= 9)
a[i][j] = j + x + v;
else
a[i][j] = j + x + v - 9;
if (a[i][j] == 10)
a[i][j] = 1;
// System.out.print(a[i][j]+" ");
}
x += 3;
if (x >= 9)
x = x - 9;
// System.out.println();
if (i == 2) {
v = 2;
x = firstval;
}
if (i == 5) {
v = 3;
x = firstval;
}
}
int eorh;
Scanner in = new Scanner(System.in);
System.out
.println("hey lets play a game of sudoku:take down the question and replace the 0's with your digits and complete the game by re entering your answer");
System.out.println("enter your option 1.hard 2.easy");
eorh = in.nextInt();
switch (eorh) {
case 1:
b[0][0] = a[0][0];
b[8][8] = a[8][8];
b[0][3] = a[0][3];
b[0][4] = a[0][4];
b[1][2] = a[1][2];
b[1][3] = a[1][3];
b[1][6] = a[1][6];
b[1][7] = a[1][7];
b[2][0] = a[2][0];
b[2][4] = a[2][4];
b[2][8] = a[2][8];
b[3][2] = a[3][2];
b[3][8] = a[3][8];
b[4][2] = a[4][2];
b[4][3] = a[4][3];
b[4][5] = a[4][5];
b[4][6] = a[4][6];
b[5][0] = a[5][0];
b[5][6] = a[5][6];
b[6][0] = a[6][0];
b[6][4] = a[6][4];
b[6][8] = a[6][8];
b[7][1] = a[7][1];
b[7][2] = a[7][2];
b[7][5] = a[7][5];
b[7][6] = a[7][6];
b[8][4] = a[8][4];
b[8][5] = a[8][5];
b[0][0] = a[0][0];
b[8][8] = a[8][8];
break;
case 2:
b[0][3] = a[0][3];
b[0][4] = a[0][4];
b[1][2] = a[1][2];
b[1][3] = a[1][3];
b[1][6] = a[1][6];
b[1][7] = a[1][7];
b[1][8] = a[1][8];
b[2][0] = a[2][0];
b[2][4] = a[2][4];
b[2][8] = a[2][8];
b[3][2] = a[3][2];
b[3][5] = a[3][5];
b[3][8] = a[3][8];
b[4][0] = a[4][0];
b[4][2] = a[4][2];
b[4][3] = a[4][3];
b[4][4] = a[4][4];
b[4][5] = a[4][5];
b[4][6] = a[4][6];
b[5][0] = a[5][0];
b[5][1] = a[5][1];
b[5][4] = a[5][4];
b[5][6] = a[5][6];
b[6][0] = a[6][0];
b[6][4] = a[6][4];
b[6][6] = a[6][6];
b[6][8] = a[6][8];
b[7][0] = a[7][0];
b[7][1] = a[7][1];
b[7][2] = a[7][2];
b[7][5] = a[7][5];
b[7][6] = a[7][6];
b[8][2] = a[8][2];
b[8][4] = a[8][4];
b[8][5] = a[8][5];
break;
default:
System.out.println("entered option is incorrect");
break;
}
for (int y = 0; y < 9; y++) {
for (int z = 0; z < 9; z++) {
System.out.print(b[y][z] + " ");
}
System.out.println("");
}
System.out.println("enter your answer");
int c[][] = new int[9][9];
for (int y = 0; y < 9; y++) {
for (int z = 0; z < 9; z++) {
c[y][z] = in.nextInt();
}
}
for (int y = 0; y < 9; y++) {
for (int z = 0; z < 9; z++)
System.out.print(c[y][z] + " ");
System.out.println();
}
int q = 0;
for (int y = 0; y < 9; y++) {
for (int z = 0; z < 9; z++)
if (a[y][z] == c[y][z])
continue;
else {
q++;
break;
}
}
if (q == 0)
System.out
.println("the answer you have entered is correct well done");
else
System.out.println("oh wrong answer better luck next time");
System.out
.println("do you want to play a different game of sudoku(1/0)");
p = in.nextInt();
firstval=r.nextInt(8);
/*if (firstval > 8)
firstval -= 9;*/
}
}
}

I think you can use a 1D array, in much the same way a 1D array can model a binary tree. For example, to look at the value below a number, add 9 to the index.
I just made this up, but could something like this work?
private boolean makePuzzle(int [] puzzle, int i)
{
for (int x = 0; x< 10 ; x++)
{
if (//x satisfies all three conditions for the current square i)
{
puzzle[i]=x;
if (i==80) return true //terminal condition, x fits in the last square
else
if makePuzzle(puzzle, i++);//find the next x
return true;
}// even though x fit in this square, an x couldn't be
// found for some future square, try again with a new x
}
return false; //no value for x fit in the current square
}
public static void main(String[] args )
{
int[] puzzle = new int[80];
makePuzzle(puzzle,0);
// print out puzzle here
}
Edit: its been a while since I've used arrays in Java, sorry if I screwed up any syntax. Please consider it pseudo code :)
Here is the code as described below in my comment.
public class Sudoku
{
public int[] puzzle = new int[81];
private void makePuzzle(int[] puzzle, int i)
{
for (int x = 1; x< 10 ; x++)
{
puzzle[i]=x;
if(checkConstraints(puzzle))
{
if (i==80)//terminal condition
{
System.out.println(this);//print out the completed puzzle
puzzle[i]=0;
return;
}
else
makePuzzle(puzzle,i+1);//find a number for the next square
}
puzzle[i]=0;//this try didn't work, delete the evidence
}
}
private boolean checkConstraints(int[] puzzle)
{
int test;
//test that rows have unique values
for (int column=0; column<9; column++)
{
for (int row=0; row<9; row++)
{
test=puzzle[row+column*9];
for (int j=0;j<9;j++)
{
if(test!=0&& row!=j&&test==puzzle[j+column*9])
return false;
}
}
}
//test that columns have unique values
for (int column=0; column<9; column++)
{
for(int row=0; row<9; row++)
{
test=puzzle[column+row*9];
for (int j=0;j<9;j++)
{
if(test!=0&&row!=j&&test==puzzle[column+j*9])
return false;
}
}
}
//implement region test here
int[][] regions = new int[9][9];
int[] regionIndex ={0,3,6,27,30,33,54,57,60};
for (int region=0; region<9;region++) //for each region
{
int j =0;
for (int k=regionIndex[region];k<regionIndex[region]+27; k=(k%3==2?k+7:k+1))
{
regions[region][j]=puzzle[k];
j++;
}
}
for (int i=0;i<9;i++)//region counter
{
for (int j=0;j<9;j++)
{
for (int k=0;k<9;k++)
{
if (regions[i][j]!=0&&j!=k&&regions[i][j]==regions[i][k])
return false;
}
}
}
return true;
}
public String toString()
{
String string= "";
for (int i=0; i <9;i++)
{
for (int j = 0; j<9;j++)
{
string = string+puzzle[i*9+j];
}
string =string +"\n";
}
return string;
}
public static void main(String[] args)
{
Sudoku sudoku=new Sudoku();
sudoku.makePuzzle(sudoku.puzzle, 0);
}
}

Try this code:
package com;
public class Suduku{
public static void main(String[] args ){
int k=0;
int fillCount =1;
int subGrid=1;
int N=3;
int[][] a=new int[N*N][N*N];
for (int i=0;i<N*N;i++){
if(k==N){
k=1;
subGrid++;
fillCount=subGrid;
}else{
k++;
if(i!=0)
fillCount=fillCount+N;
}
for(int j=0;j<N*N;j++){
if(fillCount==N*N){
a[i][j]=fillCount;
fillCount=1;
System.out.print(" "+a[i][j]);
}else{
a[i][j]=fillCount++;
System.out.print(" "+a[i][j]);
}
}
System.out.println();
}
}
}