In the blow code the inner 3rd while loop not working please tell me why ?
Here I tried with for loop by replacing the 3rd inner while loop it is working correctly but why not working with while loop .....? can you give me genuine reason...?
import java.util.Scanner;
public class MergeArray {
void arrayInitialization(Scanner arg) {
//entering test cases
System.out.println("enter test cases");
int t = arg.nextInt();
int k, l, i;
k = 0;
l = 0;
i = 0;
//outer while loop
while (t-- > 0) {
//initializing a1[]'s size
System.out.println("enter a1[]'s size");
int as1 = arg.nextInt();
int a1[] = new int[as1];
//inner while loop-1
while (as1-- > 0) {
System.out.println("enter a1[]'s elements");
a1[i] = arg.nextInt();
System.out.print(a1[i]);
i++;
}
i = 0;
//initializing a2[]'s size
System.out.println("enter a2[]'s size");
int as2 = arg.nextInt();
int a2[] = new int[as2];
//inner while loop-2
while (as2-- > 0) {
System.out.println("enter a2[]'s elements");
a2[i] = arg.nextInt();
System.out.print(a2[i]);
i++;
}
System.out.println();
int a3[] = new int[a1.length + a2.length];
int size = as1 + as2;
//inner while loop-3
while (size-- > 0) {
if (k < a1.length)
a3[l] = a1[k];
if (k < a2.length)
a3[l + 1] = a2[k];
k++;
l += 2;
}
for (int j = 0; j < (a1.length + a2.length); j++) {
System.out.print(a3[j]);
}
}
}
public static void main(String[] args) {
MergeArray ma = new MergeArray();
Scanner sc = new Scanner(System. in );
ma.arrayInitialization(sc);
}
}
I tried so much but not found solution. Here I am using while loop because I know that while loop will work fast instead of for loop.
It does not work because you are decrementing the sizes of as1 and as2. Which will be
int size = as1 + as2; // size = 0 + 0;
Instead you can make use of the array length e.g.
int size = as1.length + as2.length;
Murat K's Answer is right, but try to init the arrays like this:
//init a1
System.out.println("enter a1[]'s size");
int a1[] = new int[arg.nextInt()];
//fill a1
for (int i = 0; i < a1.length; i++) {
System.out.println("enter element " + i + " of a1[]");
a1[i] = arg.nextInt();
}
//init a2
System.out.println("enter a2[]'s size");
int a2[] = new int[arg.nextInt()];
//fill a2
for (int i = 0; i < a2.length; i++) {
System.out.println("enter element " + i + " of a2[]");
a2[i] = arg.nextInt();
}
//init a3
int a3[] = new int[a1.length + a2.length];
//merge a1 and a2 into a3
for (int i = 0; i < a1.length; i++) {
a3[i] = a1[i];
}
for (int i = 0; i < a2.length; i++) {
a3[a1.length + i] = a2[i];
}
//print
for (int i : a3) {
System.out.print(i);
}
Related
import java.util.*;
public class Combination {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number : ");
String input = sc.next();
System.out.printf("You entered: %d\n", Integer.parseInt(input));
sc.close();
int[] arr = new int[100];
for (int i = 0; i < arr.length; i++) {
arr[i] = i + 1;
}
for (int i = 0; i <= 97; i++) {
int num_i = arr[i];
for (int j = i + 1; j <= 98; j++) {
int num_j = arr[j];
for (int k = j + 1; k <= 99; k++) {
int num_k = arr[k];
if (num_i + num_j + num_k == Integer.parseInt(input))
System.out.printf("(%d, %d, %d)", num_i, num_j, num_k);
}
}
}
}
}
When I get a number input, I want to make a code that represents this number as the sum of three numbers.
The code is complete, but there are several combinations. I want to print out only one combination. How can I edit it?
First, some important suggestions:
Do not parse input inside the nested loop as it will hit the performance. Do it once outside the nested loops.
Do not close Sacnner for System.in as it also closes System.in and there is no way to open it again without restarting JVM. It means that if it is being used in some other part of your application, your application will crash.
Always follow Java naming conventions e.g. you could name numJ instead of num_j.
Coming back to your problem, there are many ways to solve it and I have listed below just a couple of them:
Use break <<label>> to exit the nested loops:
import java.util.Scanner;
public class Combination {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number : ");
String input = sc.next();
System.out.printf("You entered: %d\n", Integer.parseInt(input));
int num = Integer.parseInt(input);
int[] arr = new int[100];
for (int i = 0; i < arr.length; i++) {
arr[i] = i + 1;
}
start: for (int i = 0; i <= 97; i++) {
int numI = arr[i];
for (int j = i + 1; j <= 98; j++) {
int numJ = arr[j];
for (int k = j + 1; k <= 99; k++) {
int numK = arr[k];
if (numI + numJ + numK == num) {
System.out.printf("(%d, %d, %d)", numI, numJ, numK);
break start;
}
}
}
}
}
}
A sample run:
Enter a number : 123
You entered: 123
(1, 22, 100)
Put the logic in a method and return:
import java.util.Scanner;
public class Combination {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number : ");
String input = sc.next();
System.out.printf("You entered: %d\n", Integer.parseInt(input));
int num = Integer.parseInt(input);
printFirstCombination(num);
}
static void printFirstCombination(int num) {
int[] arr = new int[100];
for (int i = 0; i < arr.length; i++) {
arr[i] = i + 1;
}
for (int i = 0; i <= 97; i++) {
int numI = arr[i];
for (int j = i + 1; j <= 98; j++) {
int numJ = arr[j];
for (int k = j + 1; k <= 99; k++) {
int numK = arr[k];
if (numI + numJ + numK == num) {
System.out.printf("(%d, %d, %d)", numI, numJ, numK);
return;
}
}
}
}
}
}
You can create a seperate function for that and after you find a combination, print it and return there and then to the main function. In case you didn't find a combination you return 1 which can be handled in the main function,
public class Combination {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number : ");
String input = sc.next();
System.out.printf("You entered: %d\n", Integer.parseInt(input));
int res = printCombination(input);
if(res == 1) {
// Do something
}
sc.close();
}
private static int printCombination(String input) {
int[] arr = new int[100];
for (int i = 0; i < arr.length; i++) {
arr[i] = i + 1;
}
for (int i = 0; i <= 97; i++) {
int num_i = arr[i];
for (int j = i + 1; j <= 98; j++) {
int num_j = arr[j];
for (int k = j + 1; k <= 99; k++) {
int num_k = arr[k];
if (num_i + num_j + num_k == Integer.parseInt(input)) {
System.out.printf("(%d, %d, %d)", num_i, num_j, num_k);
return 0;
}
}
}
}
return 1;
}
}
I need the maximum elements position if there is more than one maximum element then the first one is to be printed.
My code prints the position of the maximum element but not the first one.
I don't understand why the last iteration is not working as I intend it to.
Please solve it using only Java.
import java.util.Scanner;
class Main {
public static void main(String[] args) {
// put your code here
Scanner sc = new Scanner(System.in);
// define lengths
int n = sc.nextInt();
int m = sc.nextInt();
// add length to matrix
int[][] matrix = new int[n][m];
// insert elements
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
matrix[i][j] = sc.nextInt();
}
}
// define max
int max = 0;
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
if (matrix[i][j] > max) {
max = matrix[i][j];
}
}
// System.out.print(i + " " + j);
}
// System.out.print(max + " ");
// print index of highest element
// int pos1 = 0;
// int pos2 = 0;
for (int i = 0; i < n; ++i) {
for (int j = 0; j < m; ++j) {
if (matrix[i][j] == max) {
System.out.print(i + " " + j);
break;
}
// pos2 += 1;
break;
}
// pos1 += 1;
// break;
}
}
}
There is no need to go through the matrix twice. When you are searching for the max, store also the coordinates of the matrix where that max was found. A code example:
import java.util.Scanner;
class Main {
public static void main(String[] args) {
// put your code here
Scanner sc = new Scanner(System.in);
// define lengths
int n = sc.nextInt();
int m = sc.nextInt();
// add length to matrix
int[][] matrix = new int[n][m];
// insert elements
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
matrix[i][j] = sc.nextInt();
}
}
// define max
int max = Integer.MIN_VALUE, row=0, col=0;
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
if (matrix[i][j] > max) {
max = matrix[i][j];
row=i;
col=j;
}
}
}
System.out.print("max: "+max + " is at: ");
System.out.print(col + " " + row); //indexes starting from zero
}
}
Create a new variable to hold the position of the max value and set it in the current loop
int max = matrix[0][0];
int[] maxPos = new int[2];
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
if (matrix[i][j] > max) {
max = matrix[i][j];
maxPos[0] = i;
maxPos[1] = j;
}
}
}
and then remove the rest of the code and print the result
System.out.printf("Max is %d and is found at [%d, %d]\n", max, maxPos[0], maxPos[1]);
just wanting to know how do i set an input range for the scanner object, which then transfers the values and inputs them into a 2d array.
I was able to set a range for random number generator but i do not know how to apply the same concept to my scanner object
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
Random random = new Random();
int rows = 3;
int columns = 5;
System.out.println("Enter array elements : ");
int arry1[][] = new int[rows][columns];
for (int i = 0; i < rows; i++)
{
for (int j = 0; j < columns-2; j++)
{
arry1[i][j] = sc.nextInt();
}
}
arry1[0][3] = random.nextInt(50-10+1)+10;
arry1[1][3] = random.nextInt(50-10+1)+10;
arry1[2][3] = random.nextInt(50-10+1)+10;
int sum1 = 0;
int sum2 = 0;
int sum3 = 0;
sum1 = arry1[0][0]+arry1[0][1]+arry1[0][2]+arry1[0][3];
sum2 = arry1[1][0]+arry1[1][1]+arry1[1][2]+arry1[1][3];
sum3 = arry1[2][0]+arry1[2][1]+arry1[2][2]+arry1[2][3];
arry1[0][4] = sum1;
arry1[1][4] = sum2;
arry1[2][4] = sum3;
System.out.print("DISPLAYING ARRAY:");
System.out.println();
for (int[] x1 : arry1) {
for (int y1 : x1) {
System.out.print(y1 + " ");
}
System.out.println();
}
}
}
Add checking if the value is within range.
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
Random random = new Random();
int rows = 3;
int columns = 5;
System.out.println("Enter array elements : ");
int arry1[][] = new int[rows][columns];
for (int i = 0; i < rows; i++) {
for (int j = 0; j < columns - 2; j++) {
int input;
do {
input = sc.nextInt();
} while (input < 0 || input > 3);
arry1[i][j] = input;
}
}
arry1[0][3] = random.nextInt(50 - 10 + 1) + 10;
arry1[1][3] = random.nextInt(50 - 10 + 1) + 10;
arry1[2][3] = random.nextInt(50 - 10 + 1) + 10;
int sum1 = 0;
int sum2 = 0;
int sum3 = 0;
sum1 = arry1[0][0] + arry1[0][1] + arry1[0][2] + arry1[0][3];
sum2 = arry1[1][0] + arry1[1][1] + arry1[1][2] + arry1[1][3];
sum3 = arry1[2][0] + arry1[2][1] + arry1[2][2] + arry1[2][3];
arry1[0][4] = sum1;
arry1[1][4] = sum2;
arry1[2][4] = sum3;
System.out.print("DISPLAYING ARRAY:");
System.out.println();
for (int[] x1 : arry1) {
for (int y1 : x1) {
System.out.print(y1 + " ");
}
System.out.println();
}
}
For some reason I can't get the count for comparisons and swap in the InsertionSort part, it just outputs zero. And when I isolate the code for it, it outputs a number of swaps and comparisons (though I don't know if it's wrong or not, probably wrong considering the number is the same for both) and the array is not sorted at all. I'm really confused as to why this isn't working, any help is greatly appreciated!
Update: The instance of bubble was being passed onto both selection and insertion, now that that's fixed turns out T also have a problem with the selection part. Any suggestions on how to fix them?
Update 2: Fixed the selection part! Still confused about insertion.
import java.util.Scanner;
public class Sorting {
public static void main(String[] args) {
int n, c;
Scanner scan = new Scanner(System.in);
System.out.print("Number of elements: ");
n = scan.nextInt();
int[] bubbleSortArray = new int[n];
int[] selectionSortArray = new int[n];
int[] insertionSortArray = new int[n];
System.out.print("Enter " + n + " elements: ");
for (c = 0; c < n; c++) {
int i = scan.nextInt();
bubbleSortArray[c] = i;
selectionSortArray[c] = i;
insertionSortArray[c] = i;
}
BubbleSort(bubbleSortArray);
SelectionSort(selectionSortArray);
InsertionSort(insertionSortArray);
}
static void BubbleSort(int[] array) {
int n = array.length;
int cm = 0;
int sw = 0;
for (int c = 0; c < (n - 1); c++) {
for (int d = 0; d < n - c - 1; d++) {
cm++;
if (array[d] > array[d + 1]) {
int swap = array[d];
array[d] = array[d + 1];
array[d + 1] = swap;
sw++;
}
}
}
System.out.print("Bubble sort: ");
for (int c = 0; c < n; c++) {
System.out.print(array[c] + " ");
}
System.out.println("- " + cm + " comparisons, " + sw + " swaps");
}
static void SelectionSort(int[] array) {
int n = array.length;
int cm = 0;
int sw = 0;
for (int c = 0; c < n - 1; c++) {
int index = c;
for (int d = c + 1; d < n; d++){
cm++;
if (array[d] < array[index])
index = d;
}
int temp = array[index];
sw++;
array[index] = array[c];
array[c] = temp;
}
System.out.print("Selection sort: ");
for (int c = 0; c < n; c++) {
System.out.print(array[c] + " ");
}
System.out.println("- " + cm + " comparisons, " + sw + " swaps");
}
static void InsertionSort(int[] array) {
int n = array.length;
int cm = 0;
int sw = 0;
for (int c = 1; c < n; c++){
int temp = array[c];
for (int d = c - 1; d > 0 && temp < array[d]; d--) {
array[d+1] = array[d];
array[d+1] = temp;
cm++;
sw++;
}
}
System.out.print("Insertion sort: ");
for (int c = 0; c < n; c++) {
System.out.print(array[c] + " ");
}
System.out.println("- " + cm + " comparisons, " + sw + " swaps");
}
}
After you are done with BubbleSort array is sorted, and you are passing that sorted instance to SelectionSort and InsertionSort.
If you want to get the results for each kind of sorts you can do :
int n, c;
Scanner scan = new Scanner(System.in);
System.out.print("Number of elements: ");
n = scan.nextInt();
int[] bubbleSortArray = new int[n];
int[] selectionSortArray = new int[n];
int[] insertionSortArray = new int[n];
System.out.print("Enter " + n + " elements: ");
for (c = 0; c < n; c++) {
int i = scan.nextInt();
bubbleSortArray[c] = i;
selectionSortArray[c] = i;
insertionSortArray[c] = i;
}
BubbleSort(bubbleSortArray);
SelectionSort(selectionSortArray);
InsertionSort(insertionSortArray);
package test1;
import java.util.Scanner;
public class Question2 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int traincars;
int maxweight;
int count = 0;
int total = 0;
maxweight = input.nextInt();
traincars = input.nextInt();
int[] trains = new int[traincars];
for(int i = 0; i < traincars; i++)
{
trains[i] = input.nextInt();
}
if (total < maxweight)
{
for(int i = 0; i < traincars; i++)
{
total = trains[i] + trains[i+1] + trains[i+2] + trains[i+3];
count++;
}
}else
{
count = count + 3;
}
System.out.println("count");
}
}
this is a really simple program but for some reason, the array for the traincars goes out of bounds..
Why is this happening?
The problem is here:
for(int i = 0; i < traincars; i++)
{
total = trains[i] + trains[i+1] + trains[i+2] + trains[i+3];
count++;
}
When i equals traincars-1 you will be accessing elements i+1, i+2. and i+3 which are out of bounds of your trains array.
If your logic is calling for calculating totals of 4 consecutive elements of the array then your for loop should stop earlier:
for(int i = 0; i < traincars - 3; i++) {...}
In the last iteration of
for(int i = 0; i < traincars; i++)
{
total = trains[i] + trains[i+1] + trains[i+2] + trains[i+3];
count++;
}
You try to access trains[i+1] and this is bigger than the length of your trains array.
To make this for loop matter you should just do the following:
for(int i = 0; i < traincars; i++)
{
total += trains[i]; //unless of course you need something else...
count++;
}