feat(line-sweep): Add 2848

See LC for unoptimized std::map implementation

C++/2848-PointsThatIntersectWithCars/Solution.cpp

@@ -0,0 +1,46 @@
+#include <array>
+#include <cstddef>
+#include <cstdlib>
+#include <vector>
+
+class Solution {
+ public:
+  int numberOfPoints(std::vector<std::vector<int>>& nums) {
+    // nums[i] = [start, end], inclusive.
+    // Line Sweep.
+    // Counting the number of points is not straightforward? Since its the
+    // implicit range from minX to maxX.
+    // Suppose at each x-coordinate we have the number of cars that cover that
+    // point.
+    // The number can only be >= 0.
+    // If it is 0, then we can conclude that this point until the next point
+    // has no cars covering (the next point must be the start of another Car)
+    // Thus, we can maintain the number of points that are NOT covered,
+    // then take (maxX - minX) which represents the total number of points,
+    // minus the sum of uncovered points.
+    //
+    // Can be further optimized by using a fixed size array of size 102, that
+    // represent the maximum number of points given by the input constraints,
+    // 1 <= start, end <= 100.
+    // That way, we can directly count the number of points with
+    // intersection > 0
+
+    // {coordinate, count}
+    std::array<int, 102> points{};
+    for (const auto& num : nums) {
+      ++points[num[0]];
+      --points[num[1] + 1];  // exclusive end
+    }
+
+    int covered = 0;
+    int cars = 0;
+    for (const auto count : points) {
+      cars += count;
+
+      if (cars) {
+        ++covered;
+      }
+    }
+    return covered;
+  }
+};

README.md

@@ -540,6 +540,7 @@ Now solving in C++. Like it.
 | 2830 | MaximizeTheProfitAsASalesman                                     |                                               [![Go](assets/go.svg)](Go/2830-MaximizeTheProfitAsASalesman/Solution.go)                                                |
 | 2832 | MaximalRangeThatEachElementIsMaximumInIt                         |                                       [![C++](assets/c++.svg)](C++/2832-MaximalRangeThatEachElementIsMaximumInIt/Solution.cpp)                                        |
 | 2838 | MaximumCoinsHeroesCanCollect                                     |                                             [![C++](assets/c++.svg)](C++/2838-MaximumCoinsHeroesCanCollect/Solution.cpp)                                              |
+| 2848 | PointsThatIntersectWithCars                                      |                                              [![C++](assets/c++.svg)](C++/2848-PointsThatIntersectWithCars/Solution.cpp)                                              |
 | 2914 | MinimumNumberOfChangesToMakeBinaryStringBeautiful                |                                   [![C++](assets/c++.svg)](C++/2914-MinimumNumberOfChangesToMakeBinaryStringBeautiful/Solution.cpp)                                   |
 | 2924 | FindChampionTwo                                                  |                                                    [![C++](assets/c++.svg)](C++/2924-FindChampionTwo/Solution.cpp)                                                    |
 | 2931 | MaximumSpendingAfterBuyingItems                                  |                                            [![C++](assets/c++.svg)](C++/2931-MaximumSpendingAfterBuyingItems/Solution.cpp)                                            |