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public static int flattenArray(int input) {
int flatLength = 0;
for (int i = 0; i < input.length; i++) {
flatLength += input[i].length;
}
int array = new int[flatLength];
int index = 0;
for (int i = 0; i < input.length; i++) {
for (int j = 0; j < input[i].length; j++) {
array[index++] = input[i][j];
}
}
return array;
}
import java.lang .*;
public class FlattenArray {
public static void main(String args) {
int arr = new int{{1, 2}, {3, 4, 5}};
int answer = flattenArray(arr);
for(int i = 0; i < answer.length; i++) {
System.out.println(answer[i]);
}
}
public static int flattenArray(int input) {
// Write your code here
int size = 0;
for(int i = 0; i < input.length; i++)
{
for(int j = 0; j < input[i].length; j++)
{
size++;
}
}
int[] array = new int[size];
int count = 0;
for(int i = 0; i < input.length; i++)
{
for(int j = 0; j < input[i].length; j++)
{
array[count] = input[i][j];
count++;
}
}
return array;
}
}
I did a separate function to find the length of the array, and some helper functions to print the array.
my code
public class FlattenArray {
public static int getSize(int[][] input) {
int size = 0;
for (int[] subArray : input) {
size += subArray.length;
}
return size;
}
public static int[] flattenArray(int[][] input) {
int length = getSize(input);
int[] flat = new int[length];
int i = 0;
for (int[] subArray : input) {
for (int x : subArray) {
flat[i] = x;
i++;
}
}
return flat;
}
public static int[] flattenArray(int[] input) {
// copy the array
int length = input.length;
int[] flat = new int[length];
for (int i = 0; i < length; i++) {
flat[i] = input[i];
}
return flat;
}
public static void printArray(int[] arr) {
System.out.print("[");
int length = arr.length;
for (int i = 0; i < length - 1; i++) {
System.out.print(arr[i]);
System.out.print(", ");
}
if (length > 0) {
System.out.print(arr[length - 1]);
}
System.out.print("]");
}
public static void printArray(int[][] arr) {
System.out.print("[");
int length = arr.length;
for (int i = 0; i < length - 1; i++) {
printArray(arr[i]);
System.out.print(", ");
}
if (length > 0) {
printArray(arr[length - 1]);
}
System.out.print("]");
}
public static void main(String[] args) {
int[][] arr = new int[][]{{1, 2}, {3, 4, 5}};
printArray(arr);
System.out.println();
int[] answer = flattenArray(arr);
printArray(answer);
System.out.println();
}
}
import java.lang .*;
import java.util.ArrayList;
public class FlattenArray {
public static void main(String[] args) {
int[][] arr = new int[][]{{1, 2}, {3, 4, 5}};
int[] answer = flattenArray(arr);
for(int i = 0; i < answer.length; i++) {
System.out.println(answer[i]);
}
}
public static int[] flattenArray(int[][] input) {
// Write your code here
ArrayList<Integer> arry = new ArrayList<>();
for(int[] a : input){
for(int b : a){
arry.add(b);
}
}
int[] c = new int[arry.size()];
for(int d = 0; d< arry.size(); d++){
c[d] = arry.get(d);
}
return c;
}
}
Using Java Streams:
import java.lang .*;
import java.util.stream.*;
import java.util.Arrays;
public class FlattenArray {
public static void main(String[] args) {
int[][] arr = new int[][]{{1, 2}, {3, 4, 5}};
int[] answer = flattenArray(arr);
for(int i = 0; i < answer.length; i++) {
System.out.println(answer[i]);
}
}
public static int[] flattenArray(int[][] input) {
return Stream.of(input)
.flatMapToInt(Arrays::stream)
.toArray();
}
}
import java.lang .*;
public class FlattenArray {
public static void main(String args) {
int arr = new int{{1, 2}, {3, 4, 5, 6}, {7, 8, 9}};
int answer = flattenArray(arr);
for(int i = 0; i < answer.length; i++) {
System.out.println(answer[i]);
}
}
public static int flattenArray(int input) {
int result = new int[0];
for (int i = 0; i < input.length; i++) {
int resultNew = new int[result.length + input[i].length];
System.arraycopy(result, 0, resultNew, 0, result.length);
System.arraycopy(input[i], 0, resultNew, result.length, input[i].length);
result = resultNew;
}
return result;
}
}
import java.lang .*;
import java.util.ArrayList;
public class FlattenArray {
public static void main(String args) {
int arr = new int{{1, 2}, {3, 4, 5}};
int answer = flattenArray(arr);
for(int i = 0; i < answer.length; i++) {
System.out.println(answer[i]);
}
}
public static int flattenArray(int input) {
// Write your code here
ArrayList list = new ArrayList();
for ( int i =0 ; i <input.length;i++){
for (int j = 0 ; j <input[i].length;j++){
list.add(input[i][j]);
}
}
int[] ans = new int [list.size()];
for ( int i = 0 ; i <ans.length;i++){
ans[i]= list.get(i);
}
return ans;
}
}
This one doesn’t use nested loops and only has a big(O) of n compared to n^2. Instead, I’ve used System.arraycopy();.
import java.lang .*;
public class FlattenArray {
public static void main(String[] args) {
int[][] arr = new int[][]{{1, 2}, {3, 4, 5}};
int[] answer = flattenArray(arr);
for(int i = 0; i < answer.length; i++) {
System.out.println(answer[i]);
}
}
public static int[] flattenArray(int[][] input) {
int totalElements = 0;
// count num of elements in each 2nd-D array to get total # elements
for (int i = 0; i < input.length; i++) {
totalElements += input[i].length;
}
// new 1-D array the length of all the total # of elements in 2-D array
int[] answer = new int[totalElements];
int index = 0;
// step through each of the 1st-D elements of the 2-D array
for (int n = 0; n < input.length; n++) {
// copy the entire 2nd-D array at 1st-D[n] of this array to the answer array
System.arraycopy(input[n], 0, answer, index, input[n].length);
// increment index counter by the length of the 2nd-D array at 1st-D[n] of this array
index += input[n].length;
}
return answer;
}
}
I tried to do it by making a version of a linked list:
public static class IntNode {
public int data;
public IntNode next;
public IntNode(int value) {
this.data = value;
this.next = null;
}
}
public static int[] flattenArray(int[][] arr) {
IntNode head = null;
IntNode current = null;
int count = 0;
for (int i = 0; i < arr.length; i++) {
for (int j = 0; j < arr[i].length; j++) {
if (current == null) {
current = new IntNode(arr[i][j]);
head = current;
}
else {
current.next = new IntNode(arr[i][j]);
current = current.next;
}
count++;
}
}
int flat[] = new int[count];
current = head;
for (int k = 0; k < count && current != null; k++) {
flat[k] = current.data;
current = current.next;
}
return flat;
}
