题目描述
题目链接: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.
例子
例子 1
Input:
path = "/home/"
Output:"/home"
Explanation: Note that there is no trailing slash after the last directory name.
例子 2
Input:
path = "/../"
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.
例子 3
Input:
path = "/home//foo/"
Output:"/home/foo"
Explanation:In the canonical path, multiple consecutive slashes are replaced by a single one.
Constraints
1 <= path.length <= 3000
- path consists of English letters, digits, period
'.'
, slash'/'
or'_'
.- path is a valid absolute Unix path.
解题思路
这道题要求化简 Unix 路径,思路比较直观。从前往后遍历遍历字符串,以 '/'
作为分隔符分割成子串,用一个栈保存文件夹,遇到 "."
保持不动,".." 则弹出最后一个文件夹,其余情况将子串压入栈中,最后从栈底开始用 '/'
连接各个文件夹即可。这里我用 vector
因为方便从前往后遍历。代码如下:
#include <string>
#include <vector>
class Solution {
public:
std::string simplifyPath(std::string path) {
std::vector<std::string> folders;
int idx = 0;
while (idx < path.length()) {
while (idx < path.length() && path[idx] == '/') idx++;
std::string f = "";
while (idx < path.length() && path[idx] != '/') {
f += path[idx];
idx++;
}
if (f == ".") {
continue;
} else if (f == "..") {
if (!folders.empty()) {
folders.pop_back();
}
} else if (f.length()) {
folders.push_back(f);
}
}
std::string result = "";
for (auto fo : folders) {
result += "/";
result += fo;
}
if (result.empty()) {
result = "/";
}
return result;
}
};
- 时间复杂度:
O(n)
- 空间复杂度:
O(n)
GitHub 代码同步地址: 71.SimplifyPath.cpp
其他题目: GitHub: Leetcode-C++-Solution 博客: Leetcode-Solutions