406. Queue Reconstruction by Height

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.

Note:
The number of people is less than 1,100.

Example

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:

Use a comparator to sort the array with two conditions:

1. Height (h) in descending order.

2. People taller than this guy (k) in ascending order.

Then we insert every people to the list according to his k value.



Code:

public class Solution {
    public int[][] reconstructQueue(int[][] people) {
        Arrays.sort(people, new Comparator<int[]>() {
            public int compare(int[] p1, int[] p2) {
                if (p1[0] != p2[0]) {
                    return p2[0] - p1[0];
                }
                return p1[1] - p2[1];
            }
        });
        List<int[]> order = new ArrayList<>();
        for (int[] p : people) {
            order.add(p[1], p);
        }
        return order.toArray(new int[people.length][]);
    }
}