71. Simplify Path

Given an absolute path for a file (Unix-style), simplify it. 

For example,
path = "/home/", => "/home"
path = "/a/./b/../../c/", => "/c"
path = "/a/../../b/../c//.//", => "/c"
path = "/a//b////c/d//././/..", => "/a/b/c"

In a UNIX-style file system, a period ('.') refers to the current directory, so it can be ignored in a simplified path. Additionally, a double period ("..") moves up a directory, so it cancels out whatever the last directory was. For more information, look here: https://en.wikipedia.org/wiki/Path_(computing)#Unix_style

Corner Cases:

• Did you consider the case where path = "/../"?
  In this case, you should return "/".
• Another corner case is the path might contain multiple slashes '/' together, such as "/home//foo/".
  In this case, you should ignore redundant slashes and return "/home/foo".

AC code:

class Solution {
public:
    string simplifyPath(string path) {
        string res, tmp;
        vector<string> stk;
        stringstream ss(path);
        while(getline(ss,tmp,'/')) {
            if (tmp == "" or tmp == ".") continue;
            if (tmp == ".." and !stk.empty()) stk.pop_back();
            else if (tmp != "..") stk.push_back(tmp);
        }
        for(auto str : stk) res += "/"+str;
        return res.empty() ? "/" : res;
    }
};

Runtime: 4 ms, faster than 99.84% of C++ online submissions for Simplify Path.

1. std::getline (string)

Get line from stream into string

Extracts characters from is and stores them into str until the delimitation character delim is found (or the newline character, ' ', for (2)).

The extraction also stops if the end of file is reached in is or if some other error occurs during the input operation.

If the delimiter is found, it is extracted and discarded (i.e. it is not stored and the next input operation will begin after it).

Note that any content in str before the call is replaced by the newly extracted sequence.

Each extracted character is appended to the string as if its member push_back was called.

Parameters

is

istream object from which characters are extracted.

str

string object where the extracted line is stored.
The contents in the string before the call (if any) are discarded and replaced by the extracted line.

2. string和stringstream用法总结