I need a little help, I made a code to read a sequence of numbers, store them in an array and then print the even ones and then odd ones, but the test has a catch where I need to change the position of two values to pass 5 and 3:

Input data: 13452

Expected output: 42153

My output: 42135

public static void main(String[] args) { Scanner input = new Scanner(System.in); int N; N = input.nextInt(); int nums[] = new int[N]; for (int i = 0; i < N; i++) { nums[i] = input.nextInt(); } for (int i = 0; i < N; i++) { if (nums[i] % 2 == 0) { System.out.print(nums[i]); System.out.println(); } } for (int i = 0; i < N; i++) { if (nums[i] % 2 != 0) { System.out.print(nums[i]); System.out.println(); } } }

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## Answer

What isn’t clear, except through what is considered your example of valid output, is when should the value of 3 and 5 (or 5 and 3) be swapped, **before** *Even & Odd* is determined or **after** *Even & Odd* is determined. Your example indicates **after** the *Even & Odd* are determined. Whichever it truly is, it’s just a matter of placing the swapping algorithm either before or after the *Even/Odd* algorithm.

The key here is to keep everything as an array throughout the *Even/Odd* algorithm instead of printing results. This can be done in a different int[] Array which can be copied over the existing array when the *Even/Odd* process is done using the Arrays#copyOf() method (or do it the long way). Why keep it all as an array? So that swapping can be done at an index level (swap by index). Swap by value can be done but there is a lot more code required since you only want to swap the first two Swap values encountered and not all of them. Here is an example:

Scanner input = new Scanner(System.in); int n; System.out.print("Enter length of Array: -> "); n = input.nextInt(); int swapA = 3; // (or 5) int swapB = 5; // (or 3) int atIndexA = -1; // Used for swapping int atIndexB = -1; // Used for swapping int tmp = -1; // Used for swapping // Create and fill Array int nums[] = new int[n]; for (int i = 0; i < n; i++) { System.out.print("Enter number #" + (i+1) + ": -> "); nums[i] = input.nextInt(); } System.out.println("Original Entry: " + Arrays.toString(nums)); /* Get the even and odd values: Even numbers are placed into a temporary array first and then the Odd numbers. EVEN Numbers: */ int[] tmpArray = new int[n]; int indexCounter = 0; for (int i = 0; i < n; i++) { if (nums[i] % 2 == 0) { tmpArray[indexCounter] = nums[i]; indexCounter++; } } // ODD Numbers: for (int i = 0; i < n; i++) { if (nums[i] % 2 != 0) { tmpArray[indexCounter] = nums[i]; indexCounter++; } } // Overwrite the nums[] array with tmpArray[]: nums = Arrays.copyOf(tmpArray, n); System.out.println("Evens & Odds: " + Arrays.toString(nums)); /* Do the required swap (if the two digits exist). Get the index values of the first two swap values. */ for (int i = 0; i < n; i++) { if (nums[i] == swapA && atIndexA == -1) { atIndexA = i; } else if (nums[i] == swapB && atIndexB == -1) { atIndexB = i; } } /* If either atIndexA or atIndexB equals -1 then one or both of the swap values do not exit within the int[] Array. */ if (atIndexA != -1 && atIndexB != -1) { tmp = nums[atIndexA]; nums[atIndexA] = nums[atIndexB]; nums[atIndexB] = tmp; } /* You can delete this...It just indicates which swap value(s) is not conatined within the int[] Array. */ if (atIndexA == -1) { System.out.println("Swap Value '" + swapA + "' is not within the Array!"); } if (atIndexB == -1) { System.out.println("Swap Value '" + swapB + "' is not within the Array!"); } // Display the overall Result. System.out.println("Numbers Swapped: " + Arrays.toString(nums));

Here is what your Console Window could display:

Enter length of Array: -> 5 Enter number #1: -> 1 Enter number #2: -> 3 Enter number #3: -> 4 Enter number #4: -> 5 Enter number #5: -> 2 Original Entry: [1, 3, 4, 5, 2] Evens & Odds: [4, 2, 1, 3, 5] Numbers Swapped: [4, 2, 1, 5, 3]