406.Queue-Reconstruction-by-Height

406. Queue Reconstruction by Height

题目地址

https://leetcode.com/problems/queue-reconstruction-by-height/

题目描述

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]]

代码

Approach #1 Greedy

1. Pick out tallest group of people and sort them in a subarray (S). Since there's no other groups of people taller than them, therefore each guy's index will be just as same as his k value.

2. For 2nd tallest group (and the rest), insert each one of them into (S) by k value. So on and so forth.

class Solution {
  public int[][] reconstructQueue(int[][] people) {
        Arrays.sort(people, (a, b) -> 
      a[0] == b[0]? a[1] - b[1] : b[0] - a[0]
    );

    List<int[]> output = new LinkedList<>();
    for (int[] p: people) {
      output.add(p[1], p);
    }

    int n = people.length;
    return output.toArray(new int[n][2]);
  }
}