Create average-height-of-buildings-in-each-segment.cpp

Author: kamyu104

C++/average-height-of-buildings-in-each-segment.cpp

@@ -0,0 +1,64 @@
+// Time:  O(nlogn)
+// Space: O(n)
+
+class Solution {
+public:
+    vector<vector<int>> averageHeightOfBuildings(vector<vector<int>>& buildings) {
+        vector<tuple<int, int, int>> points;
+        for (const auto& b : buildings) {
+            points.emplace_back(b[0], 1, b[2]);
+            points.emplace_back(b[1], -1, b[2]);
+        }
+        sort(begin(points), end(points));
+        vector<vector<int>> result;
+        int total = 0, cnt = 0;
+        int prev = -1;
+        for (const auto& [curr, c, h] : points) {
+            if (cnt && prev != curr) {
+                if (!empty(result) && result.back()[1] == prev && result.back()[2] == total / cnt) {
+                    result.back()[1] = curr;
+                } else {
+                    result.push_back({prev, curr, total / cnt});
+                }
+            }
+            total += h * c;
+            cnt += c;
+            prev = curr;
+        }
+        return result;
+    }
+};
+
+// Time:  O(nlogn)
+// Space: O(n)
+class Solution2 {
+public:
+    vector<vector<int>> averageHeightOfBuildings(vector<vector<int>>& buildings) {
+        unordered_map<int, pair<int, int>> count;
+        for (const auto& b : buildings) {
+            count[b[0]] =  {count[b[0]].first + 1, count[b[0]].second + b[2]};
+            count[b[1]] =  {count[b[1]].first - 1, count[b[1]].second - b[2]};
+        }
+        vector<tuple<int, int, int>> points;
+        for (const auto& [k, v] : count) {
+            points.emplace_back(k, v.first, v.second);
+        }
+        sort(begin(points), end(points));
+        vector<vector<int>> result;
+        int total = 0, cnt = 0;
+        int prev = -1;
+        for (const auto& [curr, c, h] : points) {
+            if (cnt) {
+                if (!empty(result) && result.back()[1] == prev && result.back()[2] == total / cnt) {
+                    result.back()[1] = curr;
+                } else {
+                    result.push_back({prev, curr, total / cnt});
+                }
+            }
+            total += h;
+            cnt += c;
+            prev = curr;
+        }
+        return result;
+    }
+};