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[Leetcode]71. Simplify Path(C++)

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:

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#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