19.2.13 [LeetCode 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.

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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"

题意

简化绝对路径，最后一个目录后不能有/

空路径写作"/"，如果要求访问根目录的上一级目录则自动简化为根目录自己，如例2

题解

 1 class Solution {
 2 public:
 3     string simplifyPath(string path) {
 4         string ans = "";
 5         int p = 0,l = path.length();
 6         while (p < l) {
 7             if (path[p] != ‘/‘) {
 8                 string menu = "";
 9                 while (p < l&&path[p] != ‘/‘)
10                     menu += path[p++];
11                 if (menu == ".")
12                     continue;
13                 else if (menu == "..") {
14                     int idx = ans.rfind(‘/‘);
15                     if (idx == string::npos)continue;
16                     ans.erase(idx);
17                 }
18                 else
19                     ans += "/" + menu;
20             }
21             p++;
22         }
23         if (ans.empty())return "/";
24         return ans;
25     }
26 };