Merge pull request #1 from gantavya12/patch-1

Create Leetcode-The-Skyline-Problem.cpp

Author: gantavyamalviya

CPP/Leetcode-The-Skyline-Problem.cpp

@@ -0,0 +1,39 @@
+class Solution {
+public:
+    vector<vector<int>> getSkyline(vector<vector<int>>& buildings) {
+        vector<vector<int>> ans;
+        multiset<int> pq{0};
+
+        vector<pair<int, int>> points;
+
+        for(auto b: buildings){
+            points.push_back({b[0], -b[2]});
+            points.push_back({b[1], b[2]});
+        }
+
+        sort(points.begin(), points.end());
+
+        int ongoingHeight = 0;
+
+        // points.first = x coordinate, points.second = height
+        for(int i = 0; i < points.size(); i++){
+            int currentPoint = points[i].first;
+            int heightAtCurrentPoint = points[i].second;
+
+            if(heightAtCurrentPoint < 0){
+                pq.insert(-heightAtCurrentPoint);
+            } else {
+                pq.erase(pq.find(heightAtCurrentPoint));
+            }
+
+            // after inserting/removing heightAtI, if there's a change
+            auto pqTop = *pq.rbegin();
+            if(ongoingHeight != pqTop){
+                ongoingHeight = pqTop;
+                ans.push_back({currentPoint, ongoingHeight});
+            }
+        }
+
+        return ans;
+    }
+};