Simplify Path

SimplifyPath.cc

// 1. 
class Solution {
public:
    string simplifyPath(string path) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<string> vec;
        int pos = path.find('/');
        while (pos != string::npos && pos < path.length()) {
            int pos2 = path.find('/', pos + 1);
            string tmp;
            if (pos2 == string::npos) {
                tmp = path.substr(pos + 1);
            } else {
                tmp = path.substr(pos + 1, pos2 - pos - 1);
            }
            if (tmp == "..") {
                if (!vec.empty()) {
                    vec.pop_back();
                }
            } else if (tmp != "." && tmp.length() > 0) {
                vec.push_back(tmp);
            }
            pos = pos2;
        }
        string ans;
        for (int i = 0; i < vec.size(); ++i) {
            ans += "/" + vec[i];
        }
        return ans.length() ? ans : "/";
    }
};

// 2.
class Solution {
public:
    string simplifyPath(string path) {
        vector<string> vec;
        int b = 0; //pointer to the first non '/' 
        int e = 0; //pointer to the first '/' or the end, 
                   //path.substr(b, e - b) is a valid segment
        while (b < path.length()) {
            while (b < path.length() && path[b] == '/') {
                ++b;
            }
            e = b + 1;
            while (e < path.length() && path[e] != '/') {
                ++e;
            }
            string t = path.substr(b, e - b);
            if (t == "..") {
                if (!vec.empty()) {
                    vec.pop_back();
                }
            } else if (t.length() && t != ".") {
                vec.push_back(t);
            }
            b = e + 1;
        }
        string ans;
        for (int i = 0; i < vec.size(); ++i) {
            ans += "/" + vec[i];
        }
        return ans.length() ? ans : "/";
    }
};


// 3.
string simplifyPath(string path) {
    vector<string> s;
    int pos1, pos2;
    pos1 = pos2 = 0;
    while (1) {
        pos2 = path.find('/', pos1);
        string ss = path.substr(pos1, pos2 - pos1);
        if (ss == ".." && !s.empty() ) {
            s.pop_back();
        } else if(ss.length() && ss != ".." && ss != "." && ss != "/") {
            s.push_back(ss);
        } 
        if (pos2 == string::npos) {
            break;
        }
        pos1 = pos2 + 1;
    }
    string ans;
    for (int i = 0; i < s.size(); ++i) {
        ans += "/" + s[i];
    }
    return ans.length() ? ans : "/";
}

// 4.
string simplifyPath(string path) {
    vector<string> ss;
    int i, last;
    for (i = 0, last = 0; i <= path.length(); ++i) {
        if (i == path.length() || path[i] == '/') {
            if (i > last) {
                string t = path.substr(last, i - last);
                if (!ss.empty() && t == "..") {
                    ss.pop_back();
                } else if (t != "." && t != "..") {
                    ss.push_back(t);
                }
            }
            last = i+1;
        }
    }
    string ans = "/";
    for (int i = 0; i < ss.size(); ++i ) {
        ans += ss[i] + "/";
    }
    return ans.length() == 1 ? ans : ans.substr(0, ans.length() - 1);
}

// 5.
string simplifyPath(string path) {
    int start_pos = path.find_first_not_of('/');
    if (start_pos == string::npos) {
        return "/";
    }
    string ret;
    for (int i = start_pos + 1; i <= path.length(); i++) {
        if (path[i] == '/' || i == path.length()) {
            string sub = path.substr(start_pos, i - start_pos);
            if (sub == "..") {
                int rpos = ret.rfind('/');
                if (string::npos != rpos) {
                    ret = ret.substr(0, rpos);
                }
            } else if (sub != ".") {
                ret += string(1, '/') + sub;
            }
            start_pos = path.find_first_not_of('/', i);
            if (start_pos == string::npos) {
                break;
            }
            i = start_pos;
        }
    }
    return ret.size() ? ret : "/";
}