K Messed Array sort in Java

Question

Given an array of integers arr where each element is at most k places away from its sorted position, code an efficient function sortKMessedArray that sorts arr. For instance, for an input array of size 10 and k = 2, an element belonging to index 6 in the sorted array will be located at either index 4, 5, 6, 7 or 8 in the input array.

Analyze the time and space complexities of your solution.

Example:

input: arr = [1, 4, 5, 2, 3, 7, 8, 6, 10, 9], k = 2

output: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Constraints:

[time limit] 5000ms

[input] array.integer arr

1 ≤ arr.length ≤ 100 [input] integer k

1 ≤ k ≤ 20 [output] array.integer

My approach improved :

import java.io.*; import java.util.*; class Solution { static int[] sortKMessedArray(int[] arr, int k) { int arrLen = arr.length; PriorityQueue<Integer> queue = new PriorityQueue<Integer>(); //Store the first k+1 elements in the heap for( int i = 0; i <= k; i++ ) queue.add(arr[i]); for( int i = k+1; i < arrLen; i++ ) { //Extract the minimum element in the priority queue arr[i - (k + 1)] = queue.poll(); //Add the next element to the queue queue.add(arr[i]); } //Extract the remaining elements from the queue and put it in the next index available for( int i = 0; i <= k; i++ ) arr[ arrLen - k - 1 + i] = queue.poll(); return arr; } public static void main(String[] args) { int [] arr = sortKMessedArray(new int[]{1,0},1); for( int m : arr ) System.out.println(m); } } 

I have the following questions regarding my approach:

1) How can I further improve my approach?

2) Is there a better way to solve this question?

3) Are there any grave code violations that I have committed?

4) Can space and time complexity be further improved?

Reference

Answer 1

You should add a bounds check that k is not larger than your array, because I don't see that explicitly mentioned in the problem statement.

for( int i = 0; i <= k; i++ ) queue.add(arr[i]); 

I think you should always add braces, but that's my personal opinion.

//Store the first k+1 elements in the heap for( int i = 0; i <= k; i++ ) queue.add(arr[i]); for( int i = k+1; i < arrLen; i++ ) { //Extract the minimum element in the priority queue arr[i - (k + 1)] = queue.poll(); //Add the next element to the queue queue.add(arr[i]); } 

This bit would make more sense if you kept i as your arr index. Then swap the statement to get rid of the +1, ...

//Store the first k+1 elements in the heap int i = 0; for(; i < k; i++ ) queue.add(arr[i]); for( ; i < arrLen; i++ ) { //Add the next element to the queue queue.add(arr[i]); //Extract the minimum element in the priority queue arr[i - k] = queue.poll(); } 

This also makes the next section pretty readable;

for( i -= k; i < arrLen; i++ ) //convert i into sorted array index by removing the k offset arr[i] = queue.poll(); 

You should also initialize the PriorityQueue with the capacity you're going to need; that's k + 1.