From 712c82aba944554a8569806cbc112f71ebc4aff7 Mon Sep 17 00:00:00 2001
From: Lam Haoyin <root@eatswap.org>
Date: Thu, 6 Jan 2022 02:00:30 +0800
Subject: [PATCH] add: 220106-CN

---
 2201/220106-CN.cpp  | 91 +++++++++++++++++++++++++++++++++++++++++++++
 2201/CMakeLists.txt |  2 +-
 2 files changed, 92 insertions(+), 1 deletion(-)
 create mode 100644 2201/220106-CN.cpp

diff --git a/2201/220106-CN.cpp b/2201/220106-CN.cpp
new file mode 100644
index 0000000..63895e1
--- /dev/null
+++ b/2201/220106-CN.cpp
@@ -0,0 +1,91 @@
+#include <string>
+#include <stack>
+#include <cstring>
+#include <iostream>
+
+/**
+ * 71. Simplify Path
+ * Given a string path, which is an absolute path (starting with a slash '/') to a file or directory in a Unix-style file system, convert it to the simplified canonical path.
+ *
+ * In a Unix-style file system, a period '.' refers to the current directory, a double period '..' refers to the directory up a level, and any multiple consecutive slashes (i.e. '//') are treated as a single slash '/'. For this problem, any other format of periods such as '...' are treated as file/directory names.
+ *
+ * The canonical path should have the following format:
+ *
+ * The path starts with a single slash '/'.
+ * Any two directories are separated by a single slash '/'.
+ * The path does not end with a trailing '/'.
+ * The path only contains the directories on the path from the root directory to the target file or directory (i.e., no period '.' or double period '..')
+ * Return the simplified canonical path.
+ */
+
+// Using pointer, in-place
+class Solution {
+public:
+	static std::string simplifyPath(const std::string& path) {
+		char* p = new char[path.length()+1];
+		std::strcpy(p, path.c_str());
+		char* r = new char[path.length()+1]{'/'};
+		for (char* current = std::strtok(p, "/"), *ptr = r; current; current = std::strtok(nullptr, "/")) {
+			if (!*current || !std::strcmp(".", current))
+				continue;
+			if (!std::strcmp("..", current)) {
+				if (ptr > r)
+					*ptr-- = 0;
+				while (ptr > r && *ptr != '/')
+					*ptr-- = 0;
+				if (ptr > r && *ptr == '/')
+					*ptr = 0;
+			}
+			else {
+				*(ptr++) = '/';
+				while (*ptr++ = *current++);
+				--ptr;
+			}
+		}
+		delete[] p;
+		std::string ret(r);
+		delete[] r;
+		return ret;
+	}
+};
+
+// Using stack
+class SolutionStack {
+public:
+	static std::string simplifyPath(const std::string& path) {
+		int len = path.length();
+		const char* pathStr = path.c_str();
+		int names[3010]{};
+		int nNames = 0;
+		for (int pos = 0; pos < len; ) {
+			for (; pathStr[pos] == '/' && pos < len; ++pos);
+			names[nNames++] = pos;
+			for (; pathStr[pos] != '/' && pos < len; ++pos);
+			names[nNames++] = pos;
+		}
+		std::stack<std::string> s;
+		for (int pos = 0; pos < nNames; pos += 2) {
+			if (names[pos + 1] - names[pos] == 0)
+				break;
+			std::string str(pathStr + names[pos], names[pos + 1] - names[pos]);
+			if (str == ".") continue;
+			if (str == "..") {
+				if (!s.empty())
+					s.pop();
+			} else {
+				s.push("/" + str);
+			}
+		}
+		std::string ret;
+		while (!s.empty()) {
+			ret = s.top().append(ret);
+			s.pop();
+		}
+		return ret.empty() ? "/" : ret;
+	}
+};
+
+int main() {
+	std::cout << Solution::simplifyPath("/a//b////c/d//././/..") << std::endl;
+	return 0;
+}
\ No newline at end of file
diff --git a/2201/CMakeLists.txt b/2201/CMakeLists.txt
index daff41d..106d2b6 100644
--- a/2201/CMakeLists.txt
+++ b/2201/CMakeLists.txt
@@ -3,4 +3,4 @@ PROJECT(2201)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2201 220105.cpp)
\ No newline at end of file
+ADD_EXECUTABLE(2201 220106-CN.cpp)
\ No newline at end of file