Leetcode: Queue Reconstruction by Height

Queue Reconstruction by Height



Similar Problems:


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]]

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.


// Blog link: https://code.dennyzhang.com/queue-reconstruction-by-height
// Basic Ideas:
//     Intuitive Idea: Find the mininum h, whose k is 0
//        Once we have identified one, 
//          we deduct k of other other items whose h is no smaller than current one
//
//     Better Idea: sort and insert
//
// [[7,0], [4,4], [7,1], [5,0], [6,1], [5,2]]
//
// sorted:
// [[7,0], [7,1], [6,1], [5,0], [5,2], [4,4]]
//
// switch:
// [[7,0], [6,1], [7,1], [5,0], [5,2], [4,4]]
// [[5,0], [7,0], [6,1], [7,1], [5,2], [4,4]]
// [[5,0], [7,0], [5,2], [6,1], [7,1], [4,4]]
// [[5,0], [7,0], [5,2], [6,1], [4,4], [7,1]]
//
// TODO: need a simple way to switch items
//
// Complexity: Time O(n*n), Space O(n)

func reconstructQueue(people [][]int) [][]int {
    res := people
    sort.Slice(people, func(i, j int) bool {
        if people[i][0] > people[j][0] {return true}
        if people[i][0] == people[j][0] && people[i][1] < people[j][1] {
            return true
        }
        return false
    })

    for i, p := range people {
        j := p[1]
        copy(res[j+1:i+1], res[j:i])
        res[j] = p
    }
    return res
}
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