Design File System

// https://leetcode.com/problems/design-file-system/description/

/*
You are asked to design a file system that allows you to create new paths and associate them with different values.

The format of a path is one or more concatenated strings of the form: / followed by one or more lowercase English letters. 
For example, "/leetcode" and "/leetcode/problems" are valid paths while an empty string "" and "/" are not.

Implement the FileSystem class:

bool createPath(string path, int value) Creates a new path and associates a value to it if possible and returns true. 
Returns false if the path already exists or its parent path doesn't exist.
int get(string path) Returns the value associated with path or returns -1 if the path doesn't exist.

Ex1:
Input:
["FileSystem","createPath","get"]
[[],["/a",1],["/a"]]
Output:
[null,true,1]
Explanation:
FileSystem fileSystem = new FileSystem();

fileSystem.createPath("/a", 1); // return true
fileSystem.get("/a"); // return 1

Ex2:
Input:
["FileSystem","createPath","createPath","get","createPath","get"]
[[],["/leet",1],["/leet/code",2],["/leet/code"],["/c/d",1],["/c"]]
Output:
[null,true,true,2,false,-1]
Explanation:
FileSystem fileSystem = new FileSystem();

fileSystem.createPath("/leet", 1); // return true
fileSystem.createPath("/leet/code", 2); // return true
fileSystem.get("/leet/code"); // return 2
fileSystem.createPath("/c/d", 1); // return false because the parent path "/c" doesn't exist.
fileSystem.get("/c"); // return -1 because this path doesn't exist.

*/

#include <vector>
#include <string>
#include <unordered_map>

using namespace std;

struct TrieNode {
    unordered_map<string, TrieNode*> child;
    bool isFile;
    int content;

    TrieNode() {
        isFile = false;
        content = -1;
    }
};

// Time: O(T) to add path to the trie if it contains T components
// Space: O(T) for each unique path.
class FileSystem {
private:
    TrieNode* root = nullptr;

    vector<string> split(string& path) {
        vector<string> result;
        string cur = "";
        for (int i = 1; i < path.size(); ++i) {
            char c = path[i];
            if (c == '/') {
                result.push_back(cur);
                cur = "";
            }
            else {
                cur.push_back(c);
            }
        }
        result.push_back(cur);
        return result;
    }

    bool insert(vector<string>& path, int value) {
        int n = path.size();
        TrieNode* cur = root;
        for (int i = 0; i < n; ++i) {
            if (cur->child.find(path[i]) == cur->child.end()) {
                if (i != n - 1) {
                    return false;
                }
                cur->child[path[i]] = new TrieNode();
            }
            else {
                if (i == n - 1) {
                    return false; // the path already exist
                }
            }
            cur = cur->child[path[i]];
        }
        cur->isFile = true;
        cur->content = value;
        return true;
    }

    int find(vector<string>& path) {
        int n = path.size();
        TrieNode* cur = root;
        for (int i = 0; i < n; ++i) {
            if (cur->child.find(path[i]) == cur->child.end()) {
                return -1;
            }
            cur = cur->child[path[i]];
        }
        return cur->content;
    }
public:
    FileSystem() {
        root = new TrieNode();
    }

    bool create(string path, int value) {
        vector<string> p = split(path);
        return insert(p, value);
    }

    int get(string path) {
        vector<string> p = split(path);
        return find(p);
    }
};```