So I have written code to give me a the smallest index of the smallest element for an array meaning that if there are doubles in my array it would give me the one with the smallest index for example :
myList = {1,3,1,4,5,5}; when running the code it would give me the index of 0 and not 2
What I am having trouble doing is converting this code for a 2d array?
My code:
public static int indexSmall(int[] array)
{
int index = 0;
int low = array[index];
for(int i = 0; i < array.length; i++)
{
if (low > array[i])
{
low = array[i];
index = i;
}
}
return index;
}
Basically the same thing but you're going to have to utilize two variables in order to keep track of the row and column indices since it is no longer one index in a 2D array that you are looking for. What you want to return is simply up to you at this point.
public static int indexSmall(int[] array)
{
int row = 0;
int col = 0;
int low = array[row][col];
for(int i = 0; i < array.length; i++) //array.length is the number of
//arrays in the 2D array aka the number of rows
{
for(int j = 0; j < array[i].length; j++) //array[i].length is the number of elements
//in one of the arrays in the 2D arrays aka
//the number of columns
{
if (low > array[i][j])
{
low = array[i][j];
row = i;
col = j
}
}
}
return row; //you can also return col or a combination of the two
}
Related
The duty of this method is to increment or add 1 to, the largest element in the array arr. If the same largest element is present more than once in the array, the last occurrence should be incremented. ("Last" means the one in the row with the largest subscript, and the one with the largest column subscript if there is more than one occurrence of the largest element in that row.) The method should not do any unnecessary work or computation. Note that the array's rows may have different numbers of elements.
Solution:
public static void incrMax(int[][] arr) {
int maxRow = 0;
int maxCol = 0;
boolean found = false;
for(int row = 0; row < arr.length; row++) {
for(int col = 0; col < arr[row].length; col++) {
if(!found || arr[row][col] >= arr[maxRow][maxCol] {
maxRow = row;
maxCol = col;
found = true;
}
if(found) {
arr[maxRow][maxCol] += 1;
}
}
}
}
What I understand is that we would want to create two int's to store the maximum elements for horizontal rows and vertical columns. In order to seek those values out we need to loop the 2D-array. I am particularly confused by nested for-loops and 2d arrays. And the line:
if(!found || arr[row][col] >= arr[maxRow][maxCol]
Can someone please walk through the logic of this code?
Thank you
void increment(int[][] mat) {
//increment the max of every row by one
for (int i = 0; i < mat.length; i++) {
int maxRow = 0, maxIndex = -1;
for (int j = 0; j < mat[i].length; j++) {
if (maxRow <= mat[i][j]) { // to allow multiple occurences of the same value i used <=
maxRow = mat[i][j];
maxIndex = j;
}
}
//we check if a max is found
if (maxIndex != -1) {
mat[i][maxIndex]++;
}
}
}
this will do the work you are asking for
I am writing a program using a method that returns the location of the largest element in a two dimensional array.
Example:
Enter the number of rows and columns of the array:
3 4
Enter the array:
23.5 35 2 10
4.5 3 45 3.5
35 44 5.5 9.6
the location of the largest element is at (1, 2)
My code is working, but I'm getting the output wrong. Instead of numbers I am getting some weird output with letters and numbers. How can I fix it? Thanks!
My code
import java.util.Scanner;
public class homework1a {
public static int[] locateLargest(double[][] a)
{
int total = 0;
int maxRow = 0;
int maxColumn = 0;
for (int i = 0; i < a.length; i++)
{
for (int j = 0; j < a[i].length; j++)
{
maxRow = i;
maxColumn = j;
}
}
int[] largest = new int[2];
largest[0] = maxRow;
largest[1] = maxColumn;
return largest;
}
public static void main(String[] args)
{
//Create Scanner
Scanner input = new Scanner(System.in);
double b = 0;
//User input rows and columns
System.out.println("Enter the number of rows and columns in the array: ");
int numberOfRows = input.nextInt();
int numberOfColumns = input.nextInt();
//User input data in array
System.out.println("Enter numbers into array: ");
//Create array
double[][] a = new double[numberOfRows][numberOfColumns];
for (int i = 0; i < a.length; i++)
{
for (int j = 0; j < a[i].length; j++)
{
a[i][j] = input.nextDouble();
}
}
System.out.println("The location of the largest element is at "+ locateLargest(a));
}
}
Your method locateLargest() returns an int-array, which you are implicitly converting to string while printing it.
I think you want to display the row and cell numbers inside the array:
int[] largest = locateLargest(a);
System.out.println(String.format("The location of the largest element is at %d,%d", largest[0], largest[1]));
locateLargest(a) returns an int[2]. Arrays cannot be converted to strings natively, so the default toString() implementation is invoked on the array. The returned string representation does not contain the array elements.
This question might help you to print a helpful representation of the array. You might also want to print both values independently, not the array as a whole, e.g. like this:
int[] pos = locateLargest(a);
System.out.println("The location of the largest element is at " + pos[0] + ":" + pos[1]);
To print Arrays use Arrays.toString(array) output will be like [x,y]
System.out.println("The location of the largest element is at "+ Arrays.toString(locateLargest(a)));
Your method locateLargest returns an int[] which will not be printed out nicely.
If you want to keep the signature of locateLargest as it is, you could change your code in main like this:
int[] positionOfLargest = locateLargest(a);
System.out.println("The location of the largest element is at " +
positionOfLargest[0] + "/" + positionOfLargest[1]);
This stores the result in positionOfLargest and then prints out x/y coordinates the way you want them.
Hey for finding largest you can have your method like this.
public static int[] locateLargest(double[][] a)
{
int maxValue = 0;
int maxRow = 0;
int maxColumn = 0;
for (int i = 0; i < a.length; i++)
{
for (int j = 0; j < a[i].length; j++)
{
If(a[i][j] > maxValue)
{
maxValue = a[i][j] ;
maxRow = i;
maxColumn = j;
}
}
}
int[] largest = new int[2];
largest[0] = maxRow;
largest[1] = maxColumn;
return largest;
}
u should edit your locateLargest as this:
public static int[] locateLargest(double[][] a)
{
//may be ur array is contain negative
//so u can not use zero as MAX it's better to use first array element
int MAX = a[0][0];
int maxRow = 0;
int maxColumn = 0;
for (int i = 0; i < a.length; i++)
{
for (int j = 0; j < a[i].length; j++)
{
if(MAx < a[i][j]){
maxRow = i;
maxColumn = j;
}
}
}
int[] largest = new int[2];
largest[0] = maxRow;
largest[1] = maxColumn;
String result="location of largest num =a["+maxRow+"]["+maxColumn+"]";
return largest;
}
I was trying to write a method that finds the largest number in a column. However, it seems that I am having problem to find a way to return the highest number in a column rather than taking into consideration all numbers combined in the array. I would really appreciate any comments or feedback!
This is my code:
public static void max1(int[][] score) {
for (int i = 0; i < score.length; i++) {
int max = score[0][0];
for (int j = 0; j < score[i].length; j++)
if (score[i][j] > max)
max = score[i][j];
System.out.println(max + " ");
}
}
You are trying to find the max in row not in column. Do some changes in your code
public static void max1(int[][] score) {
for (int i = 0; i < score[0].length; i++) { // i should be your column
int max = score[0][i];// assign 1st value of the column as max
for (int j = 0; j < score.length; j++){ // j is your row
if (score[j][i] > max){ // check the column elements instead of row elements
max = score[j][i];// get the column values
}
}
System.out.println(max + " ");
}
}
Do int max = score[0][i]; instead of int max = score[0][0]; Because if you always intialize max with score[0][0] and this int is bigger then the biggest value in a column, you will get a wrong result.
And do:
if (score[innerloop][outerloop] > max)
max = score[innerloop][outerloop];
instead of:
if (score[outerloop][innerloop] > max)
max = score[outerloop][innerloop];
That was logical failure because the first index is the column and the secound is the row.
score[0][0] = 1;
score[0][1] = 2;
score[0][2] = 3;
score[1][0] = 4;
score[1][1] = 5;
score[1][2] = 6;
score[2][0] = 7;
score[2][1] = 8;
score[2][2] = 9;
The Array now look like this matrix:
1 2 3
4 5 6
7 8 9
You want compare for example 1,4,7 so you habe to compare score[0][0], score[0][1], score[0][2]. So the secound index must be the counter of the inner for-loop.
You need to specify the index of the column you want to find the max in and loop on rows:
public static int maxCol(int [][] score, int colIndex) {
int max = score[0][colIndex];
for(int i = 0 ; i < score.length ; ++i) {
max = Math.max(max, score[i][colIndex]);
}
return max;
}
public static void max1(int[][] score) {
for (int i = 0; i < score.length; i++) {
int max = -1;
for (int j = 0; j < score[i].length; j++)
if (score[i][j] > max)
max = score[i][j];
System.out.println("max: '" + max + "'");
}
}
And perhaps you switched your columns and rows, means you have to switch the code too, happened already a lot to me. Try to check if i is your rows and j is your columns.
The following code prints the Maximum Number in each column.
public static void max1(int[][] score) {
for (int i = 0; i < score.length; i++) {
int max = Integer.MIN_VALUE; // set max to minimum value before starting loop
for (int j = 0; j < score[i].length; j++)
{
if (score[i][j] > max)
max = score[i][j];
}
System.out.println(max + " ");
}
}
First you should change the int max = score[0][0]; into as int max = Integer.MIN_VALUE; as it might produce not valid result.
And the second is that you need to swap the index while compare
if (score[j][i] > max) {
max = score[j][i];
}
static int max1(int[][] score) {
int max = score[0][0]; // set initial value to the first index in array
for (int i = 0; i < score.length; i++) { // cycle through row
for (int j = 0; j < score[i].length; j++) { // cycle through colmn
if (score[i][j] > max) { // if the index value is greater than largest number
max = score[i][j]; // make it the new index value
}
}
} return max;
}
So here's my problem. I have to write a program that will fill array with random numbers(and it's ok), then it's necessary to print only even index numbers or only odd value numbers(j). Tried like this but when i put if statement and it shows every even number (index and value-the second in array) so it wrong. What should i do so?
import java.util.Random;
public class Array {
public static void main(String[] args)
{
int rows = 5;
int colu = 2;
Random r = new Random();
int [][] array = new int [rows][colu];
for(int row = 0; row < array.length; row++)
{
for(int col = 0; col < array[row].length; col++)
{
array[row][col] = r.nextInt(10);
}
}
for(int i = 0; i < array.length; i++)
{
for(int j = 0; j < array[i].length; j++)
{
if(array[i][j]%2 == 0){
System.out.print(array[i][j] + " ");
}
}
}
System.out.println();
}
}
Thanks
I'm going to take a stab at this but I'm not sure if I quite understand yet.
int array[][] = new int[row][col];
// ... populate the array with random numbers, works fine...
// Let's traverse the first column.
for (int i = 0; i < row; i++) {
int value = array[i][0]; // col 0 means first column
if (value % 2 == 0) {
// ...
}
}
// Let's traverse the second column.
for (int i = 0; i < row; i++) {
int value = array[i][1]; // col 1 means second column
// ...
}
Is this what you mean? If it is, do you see the pattern and how you could generalize this and make the code a bit smaller?
Just implement this formula in your "if" statement :
(Number × 2 )/4 ==0. You will always get even numbers. You can handle the rest :D
This is the assignment: Write a method that sorts the elements of a matrix with 2 dimensions. For example
sort({{1,4}{2,3}})
would return a matrix
{{1,2}{3,4}}.
I dont know what im doing wrong in my code cause the output i get is 3.0, 3.0, 4.0, 4.0.
This is what i have so far any help would be appreciated.
public static void main(String[] args) {
double[][] array = { {1, 4}, {2, 3} };
double[][] new_array = sort(array);
for(int i = 0; i < array.length; i++) {
for(int j = 0; j < array.length; j++) {
System.out.print(new_array[i][j] + " ");
}
}
}
public static double[][] sort(double[][] array) {
double[] storage = new double[array.length];
for(int i = 0; i < array.length; i++) {
for(int j = 0; j < array.length; j++) {
storage[i] = array[i][j];
}
}
storage = bubSort(storage);
for(int i = 0; i < array.length; i++) {
for(int j = 0; j < array.length; j++) {
array[i][j] = storage[i];
}
}
return array;
}
public static double[] bubSort(double[] list) {
boolean changed = true;
double temp;
do {
changed = false;
for (int j = 0; j < list.length -1; j++)
if (list[j] > list[j + 1]) {
temp = list[j];
list[j] = list[j + 1];
list[j + 1] = temp;
changed = true;
}
} while (changed);
return list;
}
}
The main problem that you are experiencing is how you are copying the values from the 2d array into the 1d array. You are actually only copy two values into an array of length 2. The length of a 2d array is not the full m x n length.
I will give a small hint how you can go about copying from the 2d array into the 1d array, but it is up to you to figure out how to copy back from the 1d array into the 2d array. Also, how would you go about finding the full length of the array?
double[] storage = new double[4];//You should calculate this value
int k = 0;
for (int i = 0; i < array.length; i++) {
for (int j = 0; j < array.length; j++) {
storage[k++] = array[i][j];
}
}
Your bubble sort works fine, but then you are copying the values back wrong. Try printing the array storage after the sort and you will see that it is now correct.
You are overwriting your storage array you have it set to array[i]. Because it is in the for loop you are setting storage[0] = array[0][0] then setting storage[0] = array[0][1]. This causes you to only pick up the last number in that dimension of the array. Likewise, when you are reading them back out you are inserting the same number twice. Since 4 and 3 are the last two numbers in their respective dimensions this shows that you are sorting the array. You need a for loop for storage that is set < array.length and store your values inside that.