I need to write a program that reads an array of ints and an integer number n. The program must check how many times n occurs in the array.
Input:
The first line contains the size of the input array.
The second line contains elements of the array separated by spaces.
The third line contains n.
Output:
The result is only a single non-negative integer number.
My code:
import java.util.Scanner;
class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int len = scanner.nextInt();
int[] array = new int[len];
int n = scanner.nextInt();
for (int i = 0; i < len; i++){
array[i] = scanner.nextInt();
}
int counter = 0;
for (int i = 0; i < len; i++) {
if (array[i] == n) {
counter++;
}
}
System.out.println(counter);
}
}
Test input:
6
1 2 3 4 2 1
2
My result: 1
My question is why int n = scanner.nextInt();read "1". It should "2".
Reading the n variable was in the wrong place. The solution:
import java.util.Scanner;
class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int len = scanner.nextInt();
int[] array = new int[len];
for (int i = 0; i < len; i++){
array[i] = scanner.nextInt();
}
int counter = 0;
int n = scanner.nextInt();
for (int i = 0; i < len; i++) {
if (array[i] == n) {
counter++;
}
}
System.out.println(counter);
}
}
You should read n after you read the array like so:
Scanner scanner = new Scanner(System.in);
int len = scanner.nextInt();
int[] array = new int[len];
for (int i = 0; i < len; i++){
array[i] = scanner.nextInt();
}
int n = scanner.nextInt();
int counter = 0;
for (int i = 0; i < len; i++) {
if (array[i] == n) {
counter++;
}
}
System.out.println(counter);
Related
I have an issue where it seems like when I try to display my new array full of even numbers from the first array, it only outputs the last value? I don't see where the problem lies within the nested for loop inside my GetEven method?
package allevenproj;
import java.util.*;
public class AllEvenProj {
static int Read(int[] arr) {
Scanner scan = new Scanner(System.in);
int count = 0;
for (int i = 0; i < arr.length; i++) {
System.out.printf("Enter arr[%d]: ", i);
arr[i] = scan.nextInt();
if (arr[i] % 2 == 0) {
count++;
}
}
System.out.printf("There are %d even numbers\n", count);
return count;
}
static int[] GetEven(int[] arr, int count) {
int[] evenArr = new int[count];
for (int i = 0; i < arr.length; i++) {
for (int j = 0; j < count; j++) {
if (arr[i] % 2 == 0) {
evenArr[j] = arr[i];
}
}
}
return evenArr;
}
static void Print(int[] arr) {
for (int i = 0; i < arr.length; i++) {
System.out.println(arr[i]);
}
}
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.print("Enter size of array: ");
int n = scan.nextInt();
int[] arr = new int[n];
int a = Read(arr);
Print(GetEven(arr, a));
}
}
You'are getting only the last value because due to the inner for loop in the GetEven method: every time you do a full inner loop (you do it for every number in arr) you rewrite the whole evenArr.
So the fix is removing the inner loop:
static int[] getEven(int[] arr, int count) {
int[] evenArr = new int[count];
int j = 0;
for (int i = 0; i < arr.length; i++) {
if (arr[i] % 2 == 0) {
evenArr[j++] = arr[i];
}
}
return evenArr;
}
By the way, methods name should be lowercase. Naming conventions
As Ruben said the problem is in your loop. I took the liberty to refactor your code a bit just to show you a better approach to the problem
package allevenproj;
import java.util.*;
public class AllEvenProj {
static int[] read(int size) {
Scanner scan = new Scanner(System.in);
int[] arr = new int[size];
for (int i = 0; i < size; i++) {
System.out.printf("Enter arr[%d]: ", i);
arr[i] = scan.nextInt();
}
return arr;
}
static void print(int[] arr) {
System.out.printf("There are %d even numbers\n", arr.length);
for (int i = 0; i < arr.length; i++) {
System.out.println(arr[i]);
}
}
public static void main(String args[]) {
Scanner scan = new Scanner(System.in);
System.out.print("Enter size of array: ");
int size = scan.nextInt();
print(Arrays.stream(read(size)).filter(x -> x % 2 == 0).toArray());
}
}
I am writing the code to print a matrix on taking user input in the form of n value:
Suppose if,
n= 3
output:
3 3 3
3 0 3
3 1 3
3 2 3
3 3 3
I am getting ArrayIndexOutOfBoundException in the line: a[i][j]=n;
import java.util.*;
public class HelloWorld{
public static void main(String []args){
Scanner scan = new Scanner(System.in);
//System.out.println("Enter n");
int n = scan.nextInt();
System.out.println(n);
int a[][]= new int[n][n];
int b=0;
int mid = n/2 +1;
for(int i=0;i<n;i++)
{
for(int j=0;j<n;j++)
{
if(i+j==mid)
{
a[i][j]=n-b;
b++;
}
else
{
a[i][j]=n;
}
}
}
for(int i=0;i<n;i++)
{
for(int j=0;j<n;j++)
{
System.out.print(a[i][j]);
}
System.out.println();
}
}
}
If a request for a negative or an index greater than or equal to size of array is made, then the JAVA throws a ArrayIndexOutOfBounds Exception. This is unlike C/C++ where no index of bound check is done. TheArrayIndexOutOfBoundsException is aRuntime Exception thrown only at runtime.
Look at this line:
for(int j=0;i<n;j++)
you increment while "i < n" but you increment "j++".
When your j reaches value 3, the inner loop continues, but exceeds the array-length (of 3, because the hightest array-index is actually 2).
(Also on a minor sidenote, it is usually preferrable to write ++i or ++j within for-loop increments. This is not a rule, just easier to read for most oldscool c-Devs). Also consider leaving spaces to inprove readability:
import java.util.*;
public class HelloWorld {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
// System.out.println("Enter n");
int n = scan.nextInt();
System.out.println(n);
int a[][] = new int[n][n];
int b = 0;
int mid = n / 2 + 1;
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
if (i + j == mid) {
a[i][j] = n - b;
b++;
} else {
a[i][j] = n;
}
}
}
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
System.out.print(a[i][j]);
}
System.out.println();
}
}
minor correction in a loop
import java.util.*;
public class HelloWorld{
public static void main(String []args){
Scanner scan = new Scanner(System.in);
//System.out.println("Enter n");
int n = scan.nextInt();
System.out.println(n);
int a[][]= new int[n][n];
int b=0;
int mid = n/2 +1;
for(int i=0;i<n;i++)
{
for(int j=0;j<n;j++) //minor correction here
{
if(i+j==mid)
{
a[i][j]=n-b;
b++;
}
else
{
a[i][j]=n;
}
}
}
for(int i=0;i<n;i++)
{
for(int j=0;j<n;j++)
{
System.out.print(a[i][j]);
}
System.out.println();
}
}
}
I'm trying to create a program that asks the user to input a number which is how many random numbers between 1-100 will be generated in an array. Then I want the largest number to be swapped with the last number and the smallest number to be swapped with the first number. Here is my code so far:
import java.util.Scanner;
import java.util.Random;
public class smallbig
{
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
Random randomGenerator = new Random();
int num = scan.nextInt();
int[] myArray = new int[num];
for (int i = 0; i < myArray.length; ++i) {
int randomInt = randomGenerator.nextInt(100);
myArray[i] = randomInt;
}
int smallest = myArray[0];
int largest = myArray[0];
for (int i = 1; i < myArray.length; i++) {
if (myArray[i] > largest) {
largest = myArray[i];
}
if (myArray[i] < smallest) {
smallest = myArray[i];
}
}
for (int j = 1; j < myArray.length; j++) {
int first = myArray[0];
myArray[0] = smallest;
smallest = first;
int temp = largest;
int last = myArray.length;
myArray[last - 1] = largest;
temp = myArray[last - 1];
System.out.print(myArray[j] + " ");
}
}
}
I can't seem to get the numbers to properly swap. I created a loop which determines the smallest and largest numbers from the ones generated and these are stored. Then I create a loop which performs the necessary swaps but I can't seem to get it to work properly. It works fine for swapping the largest number with the last number but most of the time(not always) the outputted last number is also present somewhere else in the array. Here is what I mean:
input: 10
output: 62 48 34 0 91 14 64 60 91
I know there is a swapper method that I could use but I want to do it by manually swapping the numbers. Any help is appreciated, thanks.
you have one simple mistake, your loop should start from '0' when you perform the swap
for (int j = 0; j < myArray.length; j++) {
int first = myArray[0];
myArray[0] = smallest;
smallest = first;
int temp = largest;
int last = myArray.length;
myArray[last - 1] = largest;
temp = myArray[last - 1];
System.out.print(myArray[j] + " ");
Instead of a loop do
//find and stores poition of small
int smallPos = myArray.indexOf(small);
//stores tge values at 0
int tempSmall = myArray[0];
//swaps the values
myArray[0] = small;
myArray[smallPos] = smallTemp;
Just repeat this with the largest value and print it using a for loop. Tell me if it works.
I just tried this. Hope this helps.
public class App {
static int[] a = new int[100];
public static void main(String[] args) {
int i;
for(i = 0; i<a.length;i++)
a[i] = (int)(java.lang.Math.random() * 100);
int smallest = 0, largest = 0;
for(i =1; i<a.length; i++){
if(a[i] < a[smallest])
smallest = i;
if(a[i] > a[largest])
largest = i;
}
swap(0,smallest);
swap(a.length-1,largest);
for(i =0; i<a.length;i++)
System.out.print(a[i] + " ");
}
public static void swap(int i, int j){
int temp = a[i];
a[i] = a[j];
a[j] = temp;
}
}
Your last loop doesn't do anything loopy. It just does the same thing over and over. And what it does is not correct. It is swapping the smallest into the first element but it's not moving the first element anywhere: it's gone.
You need to keep track of where the largest and smallest elements were. Your swap logic doesn't take that into consideration.
Write this code
import java.util.Scanner;
import java.util.Random;
public class smallbig
{
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
Random randomGenerator = new Random();
int num = scan.nextInt();
int[] myArray = new int[num];
for (int i = 0; i < myArray.length; ++i) {
int randomInt = randomGenerator.nextInt(100);
myArray[i] = randomInt;
}
int smallest = myArray[0];
int largest = myArray[0];
int pos1,pos2;
for (int i = 1; i < myArray.length; i++) {
if (myArray[i] > largest) {
largest = myArray[i];
pos1=i;
}
if (myArray[i] < smallest) {
smallest = myArray[i];
pos2=i;
}
}
myArray[pos1]=myArray[myArray.length-1];
myArray[myArray.length-1]=largest;
myArray[pos2]=myArray[0];
myArray[0]=smallest;
for (int j = 1; j < myArray.length; j++) {
System.out.print(myArray[j] + " ");
}
}
}
i would advise against using a scanner or random values for testing since the result cannot be reproduced (at least not in an easy way). Be careful with what is an arrays index and what is the value at a specific index. This can lead to confusion very quickly. ^^
import java.util.Scanner;
import java.util.Random;
public class smallbig
{
private static int[] myArray;
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
Random randomGenerator = new Random();
//int num = scan.nextInt(); //skip this for testing ^^-d
int num = 10;
myArray = new int[num];
for (int i = myArray.length-1; i > 0; i--) {
//int randomInt = randomGenerator.nextInt(100);
int randomInt = i; //use test condition that can be reproduced!
myArray[i] = myArray.length-i;
}
int smallest = 0;
int largest = 0;
int smallestIndex = 0;
int largestIndex = 0;
for (int i = 0; i < myArray.length; i++) {
if (myArray[i] > largest) {
largest = myArray[i];
largestIndex = i;
}
if (myArray[i] < smallest) {
smallest = myArray[i];
smallestIndex = i;
}
}
switchIndexOfmyArray(0, smallestIndex);
switchIndexOfmyArray(myArray.length-1, largestIndex);
for (int j = 0; j < myArray.length; j++) {
System.out.print(myArray[j] + " ");
}
}
public static void switchIndexOfmyArray(int index, int switchWithIndex){
int temp = myArray[index];
myArray[index] = myArray[switchWithIndex];
myArray[switchWithIndex] = temp;
}
}
Yielding
0 1 8 7 6 5 4 3 2 9
I admit i was slow on this one since i am hungry and tired xD
Happy coding! ^^
You did well by finding smallest and largest. Issue was in swap. I refactor the swap method. May be it works.
import java.util.Scanner;
import java.util.Random;
public class smallbig
{
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
Random randomGenerator = new Random();
int num = scan.nextInt();
int[] myArray = new int[num];
for (int i = 0; i < myArray.length; ++i) {
int randomInt = randomGenerator.nextInt(100);
myArray[i] = randomInt;
}
for(int k=0; k < myArray.length; k++)
{
System.out.print(myArray[k] + " ");
}
System.out.println();
int smallest = myArray[0];
int largest = myArray[0];
int sIndx = 0;
int lIndx = 0;
for (int i = 1; i < myArray.length; i++) {
if (myArray[i] > largest) {
largest = myArray[i];
lIndx = i;
}
if (myArray[i] < smallest) {
smallest = myArray[i];
sIndx = i;
}
}
System.out.println();
System.out.println("Smallest = "+smallest);
System.out.println("largest = "+largest);
System.out.println("Smallest Index = "+sIndx);
System.out.println("largest Index = "+lIndx);
swapSmallAndLargest(num, myArray, sIndx, lIndx);
for(int k=0; k < myArray.length; k++)
{
System.out.print(myArray[k] + " ");
}
}
private static void swapSmallAndLargest(int num, int[] myArray, int sIndx, int lIndx) {
int temp = 0;
temp = myArray[sIndx];
myArray[sIndx] = myArray[0];
myArray[0] = temp;
temp = myArray[lIndx];
myArray[lIndx] = myArray[num-1];
myArray[num-1] = temp;
}
}
This program asks for the user to input 10 numbers and is converted into an int array. If the array is lucky (contains the numbers 7, 13, or 18) then it prints out the sum of all the numbers in the array. If it does not contain those then it is false and it only prints the sum of all the even numbers.
How do I correctly ask for this input? How do I get the sum of the even numbers in the array? Is any of the other code incorrect?
import java.util.Scanner;
public class FunArrays {
public static void main(String[] args) {
// until you do user input, you should test your methods using "test" as the input.
int[] test = {1,2,3,4,5,6,7};
luckyNumber1 = {7};
luckyNumber2 = {13};
luckyNumber3 = {18};
int[] a=new int[9];
Scanner sc=new Scanner(System.in);
System.out.println("Please enter numbers...");
for(int j=0;j==9;j++)
a[j]=sc.nextInt();
}
public static int sum(int [ ] value) {
int i, total = 0;
for(i=0; i<10; i++)
{
total = total + value[ i ];
}
return (total);
}
public static int sumOfEvens (
public static boolean isLucky (int[] array) {
if ( (int == luckyNumber1) || (int == luckyNumber2) || (int == luckyNumber3 )
return true;
else
return false
}
// write the static methods isLucky, sum, and sumOfEvens
}
You have an array of size 9. Instead it should be of size 10. So, Change the initialization to
int[] a=new int[10];
Use modulo operator % or remainder operator in Java to find out even or odd numbers.
int evenSum = 0;
for(int j=0;j<a.length;j++){
if(a[j]%2 == 0){
//even numbers
evenSum = evenSum + a[j];
}else{
//odd numbers
}
}
return evenSum;
int[] a=new int[9];
Scanner sc=new Scanner(System.in);
System.out.println("Please enter numbers...");
for(int j=0;j==9;j++)
a[j]=sc.nextInt();
}
There's something wrong with your loop, it should be
for (int j = 0; j < 9; j++)
With this fix it should correctly prompt the users for 9 numbers. Change to 10 for the array and the loop it would takes in 10 number.
Sum of evens
static int sumOfEvens(int array[]) {
int sum = 0;
for(int i = 0; i < array.length; i++>) {
if(array[i] % 2 == 0)
sum += array[i];
}
return sum;
}
Input
for(int j = 0; j < a.length; j++)
a[j] = sc.nextInt();
import java.util.Scanner;
public class MyMain1 {
public static void main(String[] args) {
// until you do user input, you should test your methods using "test" as
// the input.
int[] luckyNumbers = { 7, 13, 18 };
int[] a = new int[10];
Scanner sc = new Scanner(System.in);
System.out.println("Please enter numbers...");
for (int j = 0; j <= 9; j++) {
a[j] = sc.nextInt();
}
sc.close();
boolean sumAll = false;
for (int i : a) {
for (int j : luckyNumbers) {
if (i == j) {
sumAll = true;
break;
}
}
if(sumAll) {
break;
}
}
if (sumAll) {
System.out.println("Summing all : " + sumAll(a));
} else {
System.out.println("Summing Only Even : " + sumEven(a));
}
}
public static int sumAll(int[] value) {
int total = 0;
for (int j : value) {
total = total + j;
}
return total;
}
public static int sumEven(int[] value) {
int total = 0;
for (int j : value) {
if (j % 2 == 0) {
total = total + j;
}
}
return total;
}
}
Here is my code
import java.util.Scanner;
public class NthSmallest{
public static void main (String [] args){
Scanner input = new Scanner(System.in);
System.out.println("Please enter the size of the array");
final int N = 15;
int n = input.nextInt();
int array[] = new int [N];
System.out.println("enter 15 number ");
for (int i = 0 ; i < array.length; i++ ) {
array[i] = input.nextInt();
}
System.out.println(findNthSmallest(array, n ));
}
public static int findNthSmallest( int array[], int n ){
int i, j,t=0;
for(i = 0; i < n; i++){
for(j = 1; j < (n-i); j++){
if(array[j-1] > array[j]){
t = array[j-1];
array[j-1]=array[j];
array[j]=t;
}
}
}
return array[n-1];
}
}
When I want to find fifthSmallestNumber and enter 5 as the first input, the program finds the number five not fifth smallest number. How can I fix it?
In your for loop, it should be :
for(i = 0; i < array.length; i++){
for(j = 1; j < (array.length-i); j++){
Try this:
public static int findNthSmallest(int[] array, int n) {
Arrays.sort(array);
return array[n-1];
}