// Allison Obourn, CSE 142
// Array problems similar to problems on the final exam. 

import java.util.*;

public class ArrayPractice {
	public static void main(String[] args) {
		int[] numbers = {3, 8, 6};
		System.out.println(Arrays.toString(delta(numbers)));
		
		System.out.println(isUnique(numbers));
		int[] numbers2 = {2, 4, 6, 4, 2};
		System.out.println(isUnique(numbers2));
		
		String[] b = {"a", "b", "c", "d"};
		swapPairs(b);
		System.out.println(Arrays.toString(b));
	}
	
	// Write a static method named delta that accepts an array of integers as a 
	// parameter and returns a new array formed by inserting between each pair of 
	// values the difference between those values.  For example, given this array: 
	// int[] numbers = {3, 8, 6}; The call of delta(numbers) should return the following 
	// array: {3, 5, 8, -2, 6}
	// 0 -> 0
	// 1 -> 2
	// 2 -> 4
	public static int[] delta(int[] numbers) {
		int[] newNumbers = new int[numbers.length * 2 - 1];
		for(int i = 0; i < numbers.length - 1; i++) {
			int delta = numbers[i + 1] - numbers[i]; 
			newNumbers[i * 2] = numbers[i];
			newNumbers[i * 2 + 1] = delta;
		}
		newNumbers[newNumbers.length - 1] = numbers[numbers.length - 1];
		return newNumbers; 
	}
	
	
	// 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[] a) {
		int[] sums = new int[a.length];
		if (a.length > 0) {
			sums[0] = a[0];
			for(int i = 1; i < a.length; i++) {
				sums[i] = a[i] + sums[i - 1];
			}
		}
		return sums;
	}
	
	
	//	Write a static method called isUnique that takes an array of integers as
	// a parameter and that returns true if the values in the list are unique
	// and that returns false otherwise.  The values in the list are considered
	// unique if there is no pair of values that are equal.
	// 4 2 45 1 23 1 2 67 --> false
	public static boolean isUnique(int[] numbers) {
		for(int i = 0; i < numbers.length - 1; i++) {
			for(int j = i + 1; j < numbers.length; j++) {
				if(numbers[i] == numbers[j]) {
					return false;
				} 
			}
		}
		return true;
	}
	
	
	// Write a method named swapPairs that accepts an array of strings as a parameter 
	// and switches the order of values in a pairwise fashion. Your method should switch 
	// the order of the first two values, then switch the order of the next two, switch 
	// the order of the next two, and so on. If there are an odd number of values, the final 
	// element is not moved.
	// a b c d --> b a d c
	public static  void swapPairs(String[] a) {
		for(int i = 0; i < a.length - 1; i += 2) {
			String temp = a[i];
			a[i] = a[i + 1];
			a[i + 1] = temp;
		}
	}
	
}