From 87c808a61bb6ce46dcacf3907c4f5ebe29e60aca Mon Sep 17 00:00:00 2001
From: eat-swap <root@eatswap.org>
Date: Sat, 30 Apr 2022 01:04:28 +0800
Subject: [PATCH] add: 220429-CN [cpp]

---
 cpp/2204/220429-CN.cpp  | 49 +++++++++++++++++++++++++++++++++++++++++
 cpp/2204/CMakeLists.txt |  2 +-
 2 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 cpp/2204/220429-CN.cpp

diff --git a/cpp/2204/220429-CN.cpp b/cpp/2204/220429-CN.cpp
new file mode 100644
index 0000000..9f70298
--- /dev/null
+++ b/cpp/2204/220429-CN.cpp
@@ -0,0 +1,49 @@
+#include <cstdlib>
+#include <vector>
+#include <functional>
+
+// Definition for a QuadTree node.
+class Node {
+public:
+    bool val, isLeaf;
+    Node* topLeft;
+    Node* topRight;
+    Node* bottomLeft;
+    Node* bottomRight;
+
+	explicit Node(bool val = false, bool isLeaf = false, Node* topLeft = nullptr, Node* topRight = nullptr, Node* bottomLeft = nullptr, Node* bottomRight = nullptr) : val(val), isLeaf(isLeaf), topLeft(topLeft), topRight(topRight), bottomLeft(bottomLeft), bottomRight(bottomRight) {}
+};
+
+/**
+ * 427. Construct Quad Tree
+ * Given a n * n matrix grid of 0's and 1's only. We want to represent the grid with a Quad-Tree.
+ * Return the root of the Quad-Tree representing the grid.
+ */
+
+class Solution {
+public:
+	Node* construct(std::vector<std::vector<int>>& G) {
+		const int n = G.size();
+
+		int* prefixSum = new int[(n + 1) * (1 + n)]{};
+		for (int i = 1; i <= n; ++i)
+			for (int j = 1; j <= n; ++j)
+				prefixSum[i * n + j] = prefixSum[(i - 1) * n + j] + prefixSum[i * n + j - 1] - prefixSum[(i - 1) * n + j - 1] + G[i - 1][j - 1];
+
+		auto sum = [&](int x0, int y0, int x1, int y1) {
+			return prefixSum[x1 * n + y1] - prefixSum[x0 * n + y1] - prefixSum[x1 * n + y0] + prefixSum[x0 * n + y0];
+		};
+
+		std::function<Node*(int, int, int, int)> dfs = [&](int x0, int y0, int x1, int y1) {
+			int s = sum(x0, y0, x1, y1);
+			if (!s)
+				return new Node(false, true);
+			if (s == (y1 - y0) * (x1 - x0))
+				return new Node(true, true);
+			const int mx = (x0 + x1) >> 1, my = (y0 + y1) >> 1;
+			return new Node(std::rand() & 1, false, dfs(x0, y0, mx, my), dfs(x0, my, mx, y1), dfs(mx, y0, x1, my), dfs(mx, my, x1, y1));
+		};
+
+		return dfs(0, 0, n, n);
+	}
+};
diff --git a/cpp/2204/CMakeLists.txt b/cpp/2204/CMakeLists.txt
index 994dad8..d89f49e 100644
--- a/cpp/2204/CMakeLists.txt
+++ b/cpp/2204/CMakeLists.txt
@@ -3,4 +3,4 @@ PROJECT(2204)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2204 220429.cpp)
+ADD_EXECUTABLE(2204 220429-CN.cpp)