2271. Maximum White Tiles Covered by a Carpet

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.

class Solution {
public:
    int maximumWhiteTiles(vector<vector<int>>& tiles, int clen) {
        sort(begin(tiles), end(tiles));
        vector<int> space{0};
        int res = 0, n = tiles.size();
        for(int i = 1; i < n; i++) {
            space.push_back(space.back() + tiles[i][0] - tiles[i-1][1] - 1);
        }
        int l = 0, r = 0;
        while(r < n) {
            while(r < n and tiles[l][0] + clen > tiles[r][0]) {r++;}
            res = max(res,
                    min(tiles[l][0] + clen - 1, tiles[r-1][1]) - tiles[l][0] - (space[r-1] - space[l]) + 1
                    );
            l++;
        }
        return res;
    }
};