Java Challenge - Flatten an Array

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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();
  }
}

Manuel solution

Code
import java.lang.*;
import java.util.*;

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> output = new ArrayList<>();
    for(int i = 0; i < input.length; i++) {
      for(int j = 0; j < input[i].length; j++) {
          output.add(input[i][j]);
      }
    }
    int[] array = new int[output.size()];
    int counter = 0;
    for(int num : output){
        array[counter++] = num;
    }
    return array;
  }
}