Queue Reconstruction by Height

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2020-06-06

406. Queue Reconstruction by Height

Question:

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 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:

Using greedy, the list represents the people who has height larger or equal to current person.

class Solution {
    public int[][] reconstructQueue(int[][] people) {
        Arrays.sort(people, new Comparator<int []>(){
            @Override
            public int compare(int[] a, int[] b) {
                if (a[0] == b[0]) {
                    return a[1] - b[1];
                } else {
                    return b[0] - a[0];
                }
            }
        });
        List<int []> result = new ArrayList<int []>();
        for(int[] i : people) {
            result.add(i[1], i);
        }
        return result.toArray(new int[people.length][]);
    }
}