Compactness of a given array task

Question

I don't know if this is a duplicate, but that was the question asked to me. Given an array of random numbers and -1, placed inbetween, I need to compress the array, meaning that all -1s should be replaced, and the final result should be the last valid index with a fresh array. For instance.

Input: 3 4 -1 -1 -1 5 8 -1 8 Output: 3 4 5 8 8 5 8 -1 8 and last valid index is 4 Input: -1 -1 -1 -1 -1 2 Output: 2 -1 -1 -1 -1 2 and last valid index is 0 Input: -1 -1 -1 3 3 3 Output: 3 3 3 3 3 3 and last valid index is 2 

You should not change the values ​​only for the last valid index with the array in order to decrypt the values ​​not -1. A.

Answer 1

 int K=0 FOR i=0; i<LEN; i++ IF arr[i]!=-1 arr[K]=arr[i] K++ END IF RETURN K-1 

Answer 2

Something like that? this is php

 <?php $array = array('3','4','-1','-1','-1','5','8','-1','8'); $count = count($array); $k = 0; $i = 0; while($i < $count && $k < $count) { echo $array[$i]; if($array[$i] == '-1') { echo '|'; if ($i>=$k){$k = $i + 1;} $found = false; while($k < $count && !$found) { echo 'X'; if($array[$k] != '-1') { $array[$i] = $array[$k]; $found = true; } $k++; } } $i++; } print_r($array); echo 'Last index'.($i - 1); ?> 

Answer 3

 import java.util.Arrays; public class Compact { static int previousValid(int[] nums, int startIndex) { while (--startIndex >= 0 && nums[startIndex] == -1); return startIndex; } static int nextInvalid(int[] nums, int startIndex) { while (++startIndex < nums.length && nums[startIndex] != -1); return startIndex; } static void compact(int... nums) { int last = previousValid(nums, nums.length); for (int h = -1, t = last + 1; (h = nextInvalid(nums, h)) < (t = previousValid(nums, t)); ) { nums[last = h] = nums[t]; } System.out.println(Arrays.toString(nums) + "; last valid = " + last); } public static void main(String[] args) { compact(3, 4, -1, -1, -1, 5, 8, -1, 8); // "[3, 4, 8, 8, 5, 5, 8, -1, 8]; last valid = 4" compact(-1, -1, -1, -1, -1, 2); // "[2, -1, -1, -1, -1, 2]; last valid = 0" compact(-1, -1, -1, 3, 3, 3); // "[3, 3, 3, 3, 3, 3]; last valid = 2" compact(-1, -1, -1); // "[-1, -1, -1]; last valid = -1" compact(6, 6, 6); // "[6, 6, 6]; last valid = 2" } } 

Key ideas:

• Use previousValid and nextInvalid helper methods to make logic more understandable
• Keep track of h and t for "head" and "tail"
  • h finds nextInvalid
  • t finds previousValid
• Keep assignment nums from index t to h , and h < t