From 1032df9f650b3883b7eeb5f5f916f2cefd084311 Mon Sep 17 00:00:00 2001
From: Eat-Swap <root@eatswap.org>
Date: Mon, 23 May 2022 13:44:19 +0800
Subject: [PATCH] add: 220523-CN [cpp]

---
 cpp/2205/220523-CN.cpp  | 110 ++++++++++++++++++++++++++++++++++++++++
 cpp/2205/CMakeLists.txt |   2 +-
 2 files changed, 111 insertions(+), 1 deletion(-)
 create mode 100644 cpp/2205/220523-CN.cpp

diff --git a/cpp/2205/220523-CN.cpp b/cpp/2205/220523-CN.cpp
new file mode 100644
index 0000000..b41574f
--- /dev/null
+++ b/cpp/2205/220523-CN.cpp
@@ -0,0 +1,110 @@
+#include <vector>
+#include <cstdint>
+#include <utility>
+#include <algorithm>
+#include <functional>
+#include <queue>
+#include <iostream>
+
+/**
+ * 675. Cut Off Trees for Golf Event
+ * You are asked to cut off all the trees in a forest for a golf event. The forest is represented as an m x n matrix. In this matrix:
+ * 0 means the cell cannot be walked through.
+ * 1 represents an empty cell that can be walked through.
+ * A number greater than 1 represents a tree in a cell that can be walked through, and this number is the tree's height.
+ * In one step, you can walk in any of the four directions: north, east, south, and west. If you are standing in a cell with a tree, you can choose whether to cut it off.
+ * You must cut off the trees in order from shortest to tallest. When you cut off a tree, the value at its cell becomes 1 (an empty cell).
+ * Starting from the point (0, 0), return the minimum steps you need to walk to cut off all the trees. If you cannot cut off all the trees, return -1.
+ * You are guaranteed that no two trees have the same height, and there is at least one tree needs to be cut off.
+ */
+
+class Solution {
+private:
+	inline static int dX[] = {0, 1, 0, -1};
+	inline static int dY[] = {1, 0, -1, 0};
+
+public:
+	static int cutOffTree(const std::vector<std::vector<int>>& forest) {
+		const int m = forest.size(), n = forest.front().size();
+
+		// bit 15-8: X pos, bit 7-0: Y pos
+		std::vector<std::pair<int, uint16_t>> treePos;
+		for (int i = 0; i < m; ++i)
+			for (int j = 0; j < n; ++j)
+				if (forest[i][j] > 1)
+					treePos.emplace_back(forest[i][j], (i << 8) | j);
+		std::sort(treePos.begin(), treePos.end());
+		const int trees = treePos.size();
+
+		auto dijkstra = [&](int start) {
+			std::priority_queue<std::pair<int, int>, std::vector<std::pair<int, int>>, std::greater<>> q;
+			q.push({0, start});
+			std::vector<bool> vis(m * n);
+			std::vector<int> d(m * n, 0x7FFF0000);
+			while (!q.empty()) {
+				const auto [len, node] = q.top();
+				q.pop();
+
+				if (vis[node])
+					continue;
+
+				for (int i = 0; i < 4; ++i) {
+					int nX = dX[i] + (node / n), nY = dY[i] + (node % n);
+					if (nX < 0 || nY < 0 || nX >= m || nY >= n || !forest[nX][nY])
+						continue;
+					if (d[nX * n + nY] > 1 + d[node]) {
+						d[nX * n + nY] = 1 + d[node];
+						q.push({d[nX * n + nY], nX * n + nY});
+					}
+				}
+			}
+			return d;
+		};
+
+		auto bfs = [&](int start) {
+			std::queue<std::pair<int, int>> q;
+			q.push({0, start});
+			std::vector<bool> vis(m * n);
+			vis[start] = true;
+			std::vector<int> d(m * n, 0x7FFF0000);
+			while (!q.empty()) {
+				const auto [len, node] = q.front();
+				q.pop();
+				d[node] = len;
+				for (int i = 0; i < 4; ++i) {
+					int nX = dX[i] + (node / n), nY = dY[i] + (node % n);
+					if (nX < 0 || nY < 0 || nX >= m || nY >= n || !forest[nX][nY] || vis[nX * n + nY])
+						continue;
+					vis[nX * n + nY] = true;
+					q.push({1 + len, nX * n + nY});
+				}
+			}
+			return d;
+		};
+
+		std::vector<std::vector<int>> lengths(m * n);
+		lengths[0] = bfs(0);
+		for (int i = 1; i < m * n; ++i) {
+			if (forest[i / n][i % n] > 1)
+				lengths[i] = bfs(i);
+		}
+
+		int pos = 0, ans = 0;
+		for (const auto [h, p] : treePos) {
+			int px = (p >> 8) * n + (p & 0xFF);
+
+			if (lengths[pos][px] >= 0x7FFF0000)
+				return -1;
+
+			ans += lengths[pos][px];
+			pos = px;
+		}
+
+		return ans;
+	}
+};
+
+int main() {
+	std::cout << Solution::cutOffTree({{1,2,3},{0,0,4},{7,6,5}});
+	return 0;
+}
diff --git a/cpp/2205/CMakeLists.txt b/cpp/2205/CMakeLists.txt
index 2da5b3f..3768d0e 100644
--- a/cpp/2205/CMakeLists.txt
+++ b/cpp/2205/CMakeLists.txt
@@ -3,4 +3,4 @@ PROJECT(2205)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2205 220522.cpp)
+ADD_EXECUTABLE(2205 220523-CN.cpp)