/**
 * Created by karou on 15/09/2015.
 */
public class JavaExercises1To5 {
    /**
     *  "Global" variable used for error checking.
     *  Always check if the value is false after an input
     *  operation, otherwise the result can be incorrect!
     */
    public static boolean IOError = false;

    public static void main(String[] args) {
        ex1(new int[]{1,2,3});
        ex2(new int[] {1,2,2,4,5});
        ex3(new int[] {1,2,2,4,5,2,2,4,7,8});
        ex4(new int[]{1, 0, 1, 0, 0, 1, 1});
        ex5(new String[]{"Lorena", "Javier", "Monica"});
    }

    /**
     * Write a function such that given an int array of any length,
     * returns a new array of its first 2 elements. If the array is smaller
     * than length 2, use whatever elements are present. Test your function
     * on arrays of different size.
     *
     * Example:
     *
     * Suppose the function is called "frontPiece", then
     *
     * >frontPiece({1, 2, 3}) returns  {1, 2}
     * >frontPiece({1, 2})  returns {1, 2}
     * >frontPiece({1}) returns {1}
     */
    public static int[] ex1(int[] array) {
        if (array.length > 1) {
            return new int[]{array[0], array[1]};
        } else if (array.length == 1) {
            return new int[]{array[0]};
        } else {
            return new int[]{};
        }
    }

    /**
     * Given an int array of any length, write a function that returns true
     * if the array contains number 2 twice, and returns false otherwise.
     * Test your subroutine on  arrays of different size.
     */
    public static boolean ex2(int[] array) {
        boolean containsOnce = false;
        boolean containsTwice = false;

        for (int i = 0; i < array.length; i++) {
            if (containsTwice) break;

            if (array[i] == 2) {
                if (containsOnce) {
                    containsTwice = true;
                } else {
                    containsOnce = true;
                }
            }
        }

        return containsTwice;
    }

    /**
     * Given an array of ints, return true if the sum of all the 2's in the
     * array is exactly 8, false otherwise. Write a function to implement
     * this check.
     */
    public static boolean ex3(int[] array) {
        int sum = 0;

        for (int i = 0; i < array.length; i++) {
            if (array[i] == 2) {
                sum += 2;
            }
        }

        return sum == 8;
    }

    /**
     * Write a function such that given an array of ints returns an array
     * that contains the exact same numbers as the given array, but rearranged
     * so that all the even numbers come before all the odd numbers.
     * Other than that, the numbers can be in any order.
     *
     * Example:
     * Suppose the subroutine is called "evenOdd", then
     *
     * >evenOdd({1, 0, 1, 0, 0, 1, 1}) returns {0, 0, 0, 1, 1, 1, 1}
     * >evenOdd({3, 3, 2})  returns {2, 3, 3}
     * >evenOdd({2, 2, 2}) returns {2, 2, 2}
     */
    public static int[] ex4(int[] array) {
        int result[] = new int[array.length];

        for (int i = 0, j = 0, k = array.length - 1; i < array.length; i++) {
            if (array[i] % 2 == 0) {
                result[j] = array[i];
                j++;
            } else {
                result[k] = array[i];
                k--;
            }
        }

        return result;
    }

    /**
     * Write a function such that given an array of student names
     * (i.e. Strings) prints out the list of name that start with the
     * letter "M". Test your subroutine by writing a program that inputs
     * a list of names provided by the user and prints out the names
     * starting with letter "M".
     *
     * Example:
     *
     * >startWithM({"Musard", "John", "Marco"}) ->  The following names
     * start with "M": Musard, Marco
     * >startWithM({"Lorena", "Javier"}) ->  The array contains no names
     * starting with "M"
     * >startWithM({"Lorena", "Javier", "Monica"}) ->  There is only one name
     * starting with "M": Monica
     */
    public static void ex5(String[] names) {
        String result = "";
        String separator = ", ";
        int count = 0;

        for (int i = 0; i < names.length; i++) {
            String name = names[i];
            if (name.charAt(0) == 'M') {
                result += name + separator;
                count++;
            }
        }

        // remove last separator
        if (count > 0) result = result.substring(0, result.length() - 2);

        if (count == 0) {
            println("The array contains no names starting with \"M\"");
        } else if (count == 1) {
            println("There is only one name starting with \"M\": " + result);
        } else {
            println("The following names start with \"M\": " + result);
        }
    }

    /**
     *  Generic println.
     *  @param o object to print
     */
    public static void println(Object o) {
        System.out.println(o);
        IOError = false;
    }
}