LeetCode in Kotlin

2271. Maximum White Tiles Covered by a Carpet

Medium

You are given a 2D integer array tiles where tiles[i] = [li, ri] represents that every tile j in the range li <= j <= ri is colored white.

You are also given an integer carpetLen, the length of a single carpet that can be placed anywhere.

Return the maximum number of white tiles that can be covered by the carpet.

Example 1:

Input: tiles = [[1,5],[10,11],[12,18],[20,25],[30,32]], carpetLen = 10

Output: 9

Explanation: Place the carpet starting on tile 10.

It covers 9 white tiles, so we return 9.

Note that there may be other places where the carpet covers 9 white tiles.

It can be shown that the carpet cannot cover more than 9 white tiles.

Example 2:

Input: tiles = [[10,11],[1,1]], carpetLen = 2

Output: 2

Explanation: Place the carpet starting on tile 10.

It covers 2 white tiles, so we return 2.

Constraints:

• 1 <= tiles.length <= 5 * 104
• tiles[i].length == 2
• 1 <= li <= ri <= 109
• 1 <= carpetLen <= 109
• The tiles are non-overlapping.

Solution

import java.util.Arrays

class Solution {
    fun maximumWhiteTiles(tiles: Array<IntArray>, carpetLength: Int): Int {
        Arrays.sort(tiles, { x: IntArray, y: IntArray -> x[0].compareTo(y[0]) })
        var currentCover = Math.min(tiles[0][1] - tiles[0][0] + 1, carpetLength)
        var maxCover = currentCover
        var head = 1
        var tail = 0
        while (tail < tiles.size && head < tiles.size && maxCover < carpetLength) {
            if (tiles[head][1] - tiles[tail][0] + 1 <= carpetLength) {
                currentCover += tiles[head][1] - tiles[head][0] + 1
                maxCover = Math.max(maxCover, currentCover)
                ++head
            } else {
                val possiblePartialCoverOverCurrentHead = carpetLength - (tiles[head][0] - tiles[tail][0])
                maxCover = Math.max(maxCover, currentCover + possiblePartialCoverOverCurrentHead)
                currentCover = currentCover - (tiles[tail][1] - tiles[tail][0] + 1)
                ++tail
            }
        }
        return maxCover
    }
}

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