Valizada's blog

406. Queue Reconstruction by Height - June day 6

Link to leedcode problem definition

Suppose you have a random list of people standing in a queue. Each person is described by a pair of integers (h, k), where h is the height of the person and k is the number of people in front of this person who have a height greater than or equal to h. Write an algorithm to reconstruct the queue.

Example 1

Input:
[[7,0], [4,4], [7,1], [5,0], [6,1], [5,2]]

Output:
[[5,0], [7,0], [5,2], [6,1], [4,4], [7,1]]

Solution:

  1. Sort people:

    • Descending order by height
    • If same height -> ascending order by k-values
  2. Iterate through people
  3. Add to a list at the indexes equal to k-values
class Solution {
    public int[][] reconstructQueue(int[][] people) {        
        Arrays.sort(people, (x, y) -> {
            return x[0] == y[0]
                ? x[1] - y[1]
                : y[0] - x[0];
        });
        
        var res = new LinkedList<int[]>();
        for(var p : people) {
            res.add(p[1], p);
        }
        
        return res.toArray(new int[][]{});
    }
}