Type：medium
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 notend with a trailing /. Also, the canonical path must be the shortest string representing the absolute path.
输出最简化路径，有以下几种考虑：
1、若遇到'/'，只保留一个'/'
2、若遇到‘/../’，则回退一级目录
3、若遇到'/./'，则忽略
string simplifyPath(string path) {
int n = path.length();
string ret;
vector<string> temp;
int i = 0;
while(i < n){
while(path[i] == '/' && i < n) ++i;
if(i == n) break;
int start = i;
while(path[i] != '/' && i < n) ++i;
int end = i - 1;
string s = path.substr(start, end - start + 1);
if(s == ".."){
if(!temp.empty()) temp.pop_back();
}else if(s != "."){
temp.push_back(s);
}
}
if(temp.empty()) return "/";
for(int m = 0; m<temp.size(); ++m){
ret += '/' + temp[m];
}
return ret;
}
