Forests

Forests

using System;

// An array of integers of size n is represented by a forest aka a collection of trees.
// The tree is a n-ary tree and has the property that the parent's value is always smaller
// than its children
// Given these conditions, write a method to delete a number from this array given an index.
// This should also re-arrange the forest
// Value of each node is an index in the array
// Root nodes have the value -1
// Child nodes have the parent as the value

// Example

//      0                1  
//    /   \               \
//   2      3              4
//  arr => {-1, -1, 0, 0, 1}
//  Delete at index 0
//  Output: {-1, -1, -1, 0}
//    0   1   2  
//   /
//  3
namespace Forest
{
    public class Program
    {
        public static void Main(string[] args)
        {
            int[] input = new int[]{-1, -1, 0, 0, 1};
            var output = delete(input, 1);
            Console.WriteLine("After deleting, array is");
            foreach (var item in output)
            {
                Console.Write(item + " ");
            }   
        }
        
        static int[] delete(int[] arr, int index) 
        {
            var output = new int[arr.Length - 1];
            
            for (int i = 0; i < index; i++)
            {
                output[i] = arr[i];        
            }
            
            for(int i = index + 1; i < arr.Length; i++) 
            {
                if (arr[i] == -1 || arr[i] == index) {
                    output[i - 1] = -1;
                }  else if (arr[i] < index) {
                    output[i - 1] = arr[i];
                } else {
                    output[i - 1] = arr[i] - 1;
                }
            }
            
            return output;
        }
    }
}