test.java

test.java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * Created by madhur on 15 Aug.
 */

public class IntegerArrayFlattener {

  /**
   * Flatten an array of arbitrarily nested arrays of integers into a flat array of integers. e.g. [[1,2,[3]],4] -> [1,2,3,4].
   *
   * @param inputArray an array of Integers or nested arrays of Integers
   * @return flattened array of Integers or null if input is null
   * @throws IllegalArgumentException
   */
  public static Integer[] flatten(Object[] inputArray) throws IllegalArgumentException {

    if (inputArray == null) return null;

    List<Integer> flatList = new ArrayList<Integer>();

    for (Object element : inputArray) {
      if (element instanceof Integer) {
        flatList.add((Integer) element);
      } else if (element instanceof Object[]) {
        flatList.addAll(Arrays.asList(flatten((Object[]) element)));
      } else {
        throw new IllegalArgumentException("Input must be an array of Integers or nested arrays of Integers");
      }
    }
    return flatList.toArray(new Integer[flatList.size()]);
  }


}