// Divide and Conquer.
vector<vector<int>> ComputeSkylineInInterval(const vector<vector<int>>& buildings,
int left_endpoint, int right_endpoint) {
if (right_endpoint - left_endpoint <= 1) { // 0 or 1 skyline, just copy it.
return {buildings.cbegin() + left_endpoint,
buildings.cbegin() + right_endpoint};
}
int mid = left_endpoint + ((right_endpoint - left_endpoint) / 2);
auto left_skyline = ComputeSkylineInInterval(buildings, left_endpoint, mid);
auto right_skyline = ComputeSkylineInInterval(buildings, mid, right_endpoint);
return MergeSkylines(left_skyline, right_skyline);
}
vector<pair<int, int>> getSkyline(vector<vector<int>>& buildings) {
const auto intervals = ComputeSkylineInInterval(buildings, 0, buildings.size());
vector<pair<int, int>> res;
int last_end = -1;
for (const auto& interval : intervals) {
if (last_end != -1 && last_end < interval[start]) {
res.emplace_back(last_end, 0);
}
res.emplace_back(interval[start], interval[height]);
last_end = interval[end];
}
if (last_end != -1) {
res.emplace_back(last_end, 0);
}
return res;
}
/**
* @param buildings: A list of lists of integers
* @return: Find the outline of those buildings
*/
vector<vector<int>> buildingOutline(vector<vector<int>> &buildings) {
return ComputeSkylineInInterval(buildings, 0, buildings.size());
}