Leetcode之Simplify Path

题目：

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.

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"

代码：

string simplifyPath(string path) {
	int len = path.length();
	if (len == 0)return "/";
	string res;
	vector<string> pathelement;
	
	int i = 0;

	while (i<len) {
		while (i<len && path[i] == '/') {
			i++;
		}
		string::size_type index = path.find('/',i);
		if (index == string::npos) {
			string s = path.substr(i);
			if (s == "..") {
				if (pathelement.size() > 0) {
					pathelement.pop_back();
				}
			}
			else if (s != "."&&s!="") {
				pathelement.push_back(s);
			}
		    break;
		}
		else {
			string s = path.substr(i, index-i);
			//path = path.substr(index + 1);
			if (s == "..") {
				if (pathelement.size() > 0) {
					pathelement.pop_back();
				}
			}
			else if (s != ".") {
				pathelement.push_back(s);
			}
			i = index + 1;
		}
		
	
	}
	
	for (int i = 0; i < pathelement.size(); i++) {
		res += '/' + pathelement[i];
	}
	if (res.length() == 0)res = "/";

	return res;
}

想法：

需要考虑全面点