From b9f3d35e6836fba0b3f82776c304ab907f322883 Mon Sep 17 00:00:00 2001
From: Lam Haoyin <root@eatswap.org>
Date: Tue, 8 Feb 2022 11:48:37 +0800
Subject: [PATCH] add: 220208-CN

---
 2202/220208-CN.cpp  | 93 +++++++++++++++++++++++++++++++++++++++++++++
 2202/CMakeLists.txt |  2 +-
 2 files changed, 94 insertions(+), 1 deletion(-)
 create mode 100644 2202/220208-CN.cpp

diff --git a/2202/220208-CN.cpp b/2202/220208-CN.cpp
new file mode 100644
index 0000000..422c2bd
--- /dev/null
+++ b/2202/220208-CN.cpp
@@ -0,0 +1,93 @@
+#include <vector>
+#include <iostream>
+#include <unordered_set>
+
+/**
+ * 1001. Grid Illumination
+ * There is a 2D grid of size n x n where each cell of this grid has a lamp that is initially turned off.
+ * You are given a 2D array of lamp positions lamps, where lamps[i] = [rowi, coli] indicates that the lamp at grid[rowi][coli] is turned on. Even if the same lamp is listed more than once, it is turned on.
+ * When a lamp is turned on, it illuminates its cell and all other cells in the same row, column, or diagonal.
+ * You are also given another 2D array queries, where queries[j] = [rowj, colj]. For the jth query, determine whether grid[rowj][colj] is illuminated or not. After answering the jth query, turn off the lamp at grid[rowj][colj] and its 8 adjacent lamps if they exist. A lamp is adjacent if its cell shares either a side or corner with grid[rowj][colj].
+ * Return an array of integers ans, where ans[j] should be 1 if the cell in the jth query was illuminated, or 0 if the lamp was not.
+ *
+ * Overall time complexity: O(Max{m, n}), m = queries.size, n = lamp.size
+ */
+
+class Solution {
+private:
+	inline static constexpr unsigned long long hash(int x, int y) {
+		return (((unsigned long long) x) << 32) + ((unsigned long long) y);
+	}
+
+	inline static void unHash(const unsigned long long n, int& x, int& y) {
+		y = (n & 0xFFFFFFFFLL);
+		x = (n >> 32);
+	}
+
+	template<typename T>
+	inline static void eraseOne(std::unordered_multiset<T>& s, const T& toErase) {
+		s.erase(s.find(toErase));
+	}
+
+	inline static int directions[] = {-1, 0, 1};
+
+public:
+	static std::vector<int> gridIllumination(int n, const std::vector<std::vector<int>>& lamps, const std::vector<std::vector<int>>& queries) {
+		std::unordered_set<unsigned long long> points;
+		std::unordered_multiset<int> horizontal, vertical, diagonal, subDiagonal;
+
+		// Time complexity: O(n)
+		points.reserve(lamps.size());
+		for (const auto& i : lamps) {
+			points.insert(hash(i[0], i[1]));
+		}
+
+		// Main diagonal: (i - j) is fixed.
+		// Sub diagonal:  (i + j) is fixed.
+		// Time complexity: O(4 * n) --> O(n)
+		int x, y;
+		horizontal.reserve(points.size());
+		vertical.reserve(points.size());
+		diagonal.reserve(points.size());
+		subDiagonal.reserve(points.size());
+		for (const auto& i : points) {
+			unHash(i, x, y);
+			horizontal.insert(x);
+			vertical.insert(y);
+			diagonal.insert(x - y);
+			subDiagonal.insert(x + y);
+		}
+
+		std::vector<int> ret;
+		ret.reserve(queries.size());
+		// time complexity: O(m), m = queries.length;
+		for (const auto& i : queries) {
+			x = i[0];
+			y = i[1];
+
+			// check if affected, time complexity = O(1)
+			ret.push_back((horizontal.count(x) || vertical.count(y) || diagonal.count(x - y) || subDiagonal.count(x + y)) ? 1 : 0);
+
+			// erase effects, time complexity = O(1)
+			for (int dx : directions) {
+				for (int dy : directions) {
+					if (points.count(hash(x + dx, y + dy))) {
+						points.erase(hash(x + dx, y + dy));
+						eraseOne(horizontal, x + dx);
+						eraseOne(vertical, y + dy);
+						eraseOne(diagonal, (x + dx) - (y + dy));
+						eraseOne(subDiagonal, (x + dx) + (y + dy));
+					}
+				}
+			}
+		}
+		return ret;
+	}
+};
+
+int main() {
+	const auto ret = Solution::gridIllumination(5,{{0,0},{0,4}},{{0,4},{0,1},{1,4}});
+	for (const auto& i : ret)
+		std::cout << i << ' ';
+	return 0;
+}
diff --git a/2202/CMakeLists.txt b/2202/CMakeLists.txt
index 7bae653..bb4e559 100644
--- a/2202/CMakeLists.txt
+++ b/2202/CMakeLists.txt
@@ -3,4 +3,4 @@ PROJECT(2202)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2202 220208.cpp)
+ADD_EXECUTABLE(2202 220208-CN.cpp)