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71. Simplify Path
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.
Input: "/home/" Output: "/home" Explanation: Note that there is no trailing slash after the last directory name.
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.
Input: "/home//foo/" Output: "/home/foo" Explanation: In the canonical path, multiple consecutive slashes are replaced by a single one.
Input: "/a/./b/../../c/" Output: "/c"
Input: "/a/../../b/../c//.//" Output: "/c"
Input: "/a//b////c/d//././/.." Output: "/a/b/c"
参考资料
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"
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/**
* Runtime: 5 ms, faster than 71.14% of Java online submissions for Simplify Path.
* Memory Usage: 39.9 MB, less than 6.67% of Java online submissions for Simplify Path.
*
* @author D瓜哥 · https://www.diguage.com
* @since 2020-02-04 16:15
*/
public String simplifyPath(String path) {
String[] paths = path.split("/");
Deque<String> stack = new LinkedList<>();
for (String subpath : paths) {
if ("..".equals(subpath) && !stack.isEmpty()) {
stack.removeLast();
continue;
}
if (subpath.length() > 0 && !".".equals(subpath) && !"..".equals(subpath)) {
stack.addLast(subpath);
}
}
StringBuilder result = new StringBuilder();
while (!stack.isEmpty()) {
String name = stack.removeFirst();
result.append("/").append(name);
}
return result.length() > 0 ? result.toString() : "/";
}
/**
* Runtime: 3 ms, faster than 97.40% of Java online submissions for Simplify Path.
* Memory Usage: 39.4 MB, less than 20.00% of Java online submissions for Simplify Path.
*/
public String simplifyPathLoop(String path) {
if (Objects.isNull(path)) {
return "/";
}
Deque<String> stack = new LinkedList<>();
int i = 0;
while (i < path.length()) {
if (path.charAt(i) == '/') {
i++;
continue;
}
StringBuilder sb = new StringBuilder();
while (i < path.length() && (path.charAt(i) != '.' && path.charAt(i) != '/')) {
sb.append(path.charAt(i));
i++;
}
if (sb.length() > 0) {
stack.addLast(sb.toString());
continue;
}
while (i < path.length() && path.charAt(i) != '/') {
sb.append(path.charAt(i));
i++;
}
String strings = sb.toString();
if (sb.length() == 2 && !stack.isEmpty() && "..".equals(strings)) {
stack.removeLast();
}
if (sb.length() > 2 || (sb.length() == 2 && !"..".equals(strings))) {
stack.addLast(strings);
}
}
if (stack.isEmpty()) {
return "/";
}
StringBuilder result = new StringBuilder();
while (!stack.isEmpty()) {
String name = stack.removeFirst();
result.append("/").append(name);
}
return result.length() > 0 ? result.toString() : "/";
}