/*

* https://leetcode-cn.com/problems/simplify-path/submissions/

以 Unix 风格给出一个文件的绝对路径，你需要简化它。或者换句话说，将其转换为规范路径。

在 Unix 风格的文件系统中，一个点（.）表示当前目录本身；此外，两个点 （..） 表示将目录切换到上一级（指向父目录）；两者都可以是复杂相对路径的组成部分。更多信息请参阅：Linux / Unix中的绝对路径 v(https://blog.csdn.net/u011327334/article/details/50355600)

请注意，返回的规范路径必须始终以斜杠 / 开头，并且两个目录名之间必须只有一个斜杠 /。最后一个目录名（如果存在）不能以 / 结尾。此外，规范路径必须是表示绝对路径的最短字符串。

示例 1：

输入："/home/"

输出："/home"

解释：注意，最后一个目录名后面没有斜杠。

示例 2：

输入："/../"

输出："/"

解释：从根目录向上一级是不可行的，因为根是你可以到达的最高级。

示例 3：

输入："/home//foo/"

输出："/home/foo"

解释：在规范路径中，多个连续斜杠需要用一个斜杠替换。

示例 4：

输入："/a/./b/../../c/"

输出："/c"

示例 5：

输入："/a/../../b/../c//.//"

输出："/c"

示例 6：

输入："/a//b////c/d//././/.."

输出："/a/b/c"

-----------------------------------------------------------------------------------------------------------------------

Given an absolute path for a file (Unix-style), simplify it. Or in other words, convert it to the canonical path.

In a UNIX-style file system, a period . refers to the current directory. Furthermore, a double period .. moves the directory up a level. For more information, see: Absolute path vs relative path in Linux/Unix

Note that the returned canonical path must always begin with a slash /, and there must be only a single slash / between two directory names. The last directory name (if it exists) must not end with a trailing /. Also, the canonical path must be the shortest string representing the absolute path.

Example 1:

Input: "/home/"

Output: "/home"

Explanation: Note that there is no trailing slash after the last directory name.

Example 2:

Input: "/../"

Output: "/"

Explanation: Going one level up from the root directory is a no-op, as the root level is the highest level you can go.

Example 3:

Input: "/home//foo/"

Output: "/home/foo"

Explanation: In the canonical path, multiple consecutive slashes are replaced by a single one.

Example 4:

Input: "/a/./b/../../c/"

Output: "/c"

Example 5:

Input: "/a/../../b/../c//.//"

Output: "/c"

Example 6:

Input: "/a//b////c/d//././/.."

` Output: "/a/b/c"

*/

class MySolution {

public String simplifyPath(String path) {

Stack<String> blocks = new Stack<>();

int len = path.length();

int i = 0, start = 0;

while (i < path.length()) {

// 舍去重复的 '/'

while (i < len && path.charAt(i) == '/') {

start = i;

i++;

}

if (i + 1 < len && path.charAt(i + 1) == '/' || i == len - 1) {

String block = path.substring(start, i + 1);

// block 不会等于 "/", 所以 block 的值只有三种情况："/." "/.." "/xxxxx"

if (block.equals("/..")) {

if (!blocks.isEmpty())

blocks.pop();

}

else if (!block.equals("/."))

blocks.push(block);

}

i++;

}

String simPath = toPath(blocks);

if (simPath.equals(""))

return "/";

return simPath;

}

private String toPath(Stack<String> blocks) {

StringBuilder path = new StringBuilder();

for (String block : blocks)

path.append(block);

return path.toString();

}

}

class Solution1 {

public String simplifyPath(String path) {

int len = path.length();

LinkedList<String> s = new LinkedList<>();

for (int i = 0; i < len; i++) {

if (path.charAt(i) != '/') {

int nextIndex = path.indexOf('/', i);

String filename = nextIndex == -1 ? path.substring(i) : path.substring(i, nextIndex);

if (filename.equals("..")) {

if (!s.isEmpty())

s.poll();

} else if (!filename.equals("."))

s.addFirst(filename);

i = nextIndex;

if (i == -1)

break;

}

}

StringBuilder sb = new StringBuilder();

while (!s.isEmpty()) {

sb.append("/" + s.removeLast());

}

String res = sb.toString();

return res.equals("") ? "/" : res;

}

}