// This class contains several small examples of array manipulation.
// Each is written as a method.  The main method includes some sample
// client code.

import java.util.*;

public class ArraySample3 {
    public static void main(String[] args) {
        int[] list1 = {12, 8, 4, 0, 208, 14, 42, 38, 72, 96, 102};
        int[] list2 = {84, 42, 92, 96, 2, 4, 8, 0, 72, 302, 17, 408};

        System.out.println("list1 = " + Arrays.toString(list1));
        System.out.println("list2 = " + Arrays.toString(list2));

        System.out.println("allEven(list1) returns " + allEven(list1));
        System.out.println("allEven(list2) returns " + allEven(list2));

        int[] sum = runningSum(list1);
        System.out.println("runningSum(list1) returns " +
                           Arrays.toString(sum));
        sum = runningSum(list2);
        System.out.println("runningSum(list2) returns " +
                           Arrays.toString(sum));

        int[] result1 = interleave(list1, list2);
        int[] result2 = interleave(list2, list1);
        System.out.println("interleave(list1, list2) = " + 
                           Arrays.toString(result1));
        System.out.println("interleave(list2, list1) = " + 
                           Arrays.toString(result2));
    }

    // Write a static method called allEven that takes an array of
    // integers as a parameter and that returns true if all the integers
    // are even and that returns false otherwise
    public static boolean allEven(int[] list) {
        for (int i = 0; i < list.length; i++) {
            if (list[i] % 2 != 0) {
                return false;
            }
        }
        return true;
    }

    // Write a static method called runningSum that takes an array of
    // integers as a parameter and that returns a new array that
    // contains the running sum of the numbers in the array (where the
    // i-th value of the new array is the sum of the first i values of
    // the original array)
    public static int[] runningSum(int[] list) {
        int[] result = new int[list.length];
        if (list.length > 0) {
            result[0] = list[0];
            for (int i = 1; i < list.length; i++) {
                result[i] = list[i] + result[i - 1];
            }
        }
        /*
        alternative solution:

        int sum = 0;
        for (int i = 0; i < list.length; i++) {
            sum = sum + list[i];
            result[i] = sum;
        }
        */
        return result;
    }

    // Write a static method called interleave that takes two arrays of
    // integers as parameters and that returns a new array that contains
    // the result of interleaving the elements of the two arrays.  Two
    // arrays are interleaved by taking elements in an alternating
    // fashion from the two lists (first value of first list, first
    // value of second list, second value of first list, second value of
    // second list, etc).  If one list is longer than the other, ignore
    // the extra values.
    public static int[] interleave(int[] list1, int[] list2) {
        int min = Math.min(list1.length, list2.length);
        int[] result = new int[2 * min];
        for (int i = 0; i < min; i++) {
            result[2 * i] = list1[i];      // put list1[i] into the result
            result[2 * i + 1] = list2[i];  // put list2[i] into the result
        }
        return result;
    }
}