没看题解, 独立拗了两个小时才写完…

#include <bits/stdc++.h>

using namespace std;

typedef long long LL;

class File {
public:
    bool isFolder;
    string name;
    LL size; // size of the file, enabled only if it is file
    LL cd; // current direct size, enabled only if it is folder
    LL cr; // current recursive size
    LL LD;
    LL LR;
    map<string, File*> subFiles;
    void deleteSubFolder() {
        for (auto p: subFiles) {
            p.second->deleteSubFolder();
        }
        for (auto p: subFiles) {
            delete p.second;
        }
    }
    File(bool _isFolder, string _name, LL _size)
    {
        this->isFolder = _isFolder;
        this->name = _name;
        this->size = _size;
        this->cd = this->cr = 0;
        this->LD = this->LR = 0;
    }
};

class FS {
    File *root;
    vector<string> splitPath(string path) {
        int l = 0, r = 0;
        vector<string> ret;
        int n = path.length();
        while(r < n) {
            if (path[r] != '/') {
                ++r;
            }
            else {
                // [l, r)
                if (l != r) ret.push_back(path.substr(l, r - l));
                r++;
                l = r;
            }
        }
        if (l != r) {
            ret.push_back(path.substr(l, r - l));
        }
        return ret;
    }
public:
    FS() {
        root = new File(true, "root", 0);
    }
    bool newFile(string path, LL size) {
        vector<string> p = splitPath(path);
        LL prevSize = 0;
        // check if the name is used
        File *cur = root;
        for (int i = 0; i < p.size(); i++) {
            if (cur->subFiles.find(p[i]) != cur->subFiles.end()) {
                // exists
                if (i == p.size() - 1) {
                    if (cur->subFiles[p[i]]->isFolder) {
                        return false;
                    }
                    else {
                        // the file already exists, so is update, not new
                        prevSize = cur->subFiles[p[i]]->size;
                    }
                }
                else {
                    if (!cur->subFiles[p[i]]->isFolder) {
                        return false;
                    }
                    else {
                        cur = cur->subFiles[p[i]];
                    }
                }
            }
            else {
                // need to create
                break;
            }
        }
        // check quota
        cur = root;
        for (int i = 0; i < p.size(); i++) {
            if (i == p.size() - 1 && cur->LD != 0 && cur->cd + size - prevSize > cur->LD) return false;
            if (cur->LR != 0 && cur->cr + size - prevSize > cur->LR) return false;
            if (cur->subFiles.find(p[i]) != cur->subFiles.end()) cur = cur->subFiles[p[i]];
            else break;
        }
        // create subFolders
        cur = root;
        for (int i = 0; i < p.size() - 1; i++) {
            if (cur->subFiles.find(p[i]) == cur->subFiles.end()) {
                // need to create subfolder
                cur->subFiles[p[i]] = new File(true, p[i], 0);
            }
            cur = cur->subFiles[p[i]];
        }
        // create file
        cur = root;
        for (int i = 0; i < p.size() - 1; i++) {
            cur->cr += (size - prevSize);
            cur = cur->subFiles[p[i]];
        }
        if (cur->subFiles.find(p.back()) != cur->subFiles.end()) {
            // so the file already exists
            cur->cd += (size - prevSize);
            cur->cr += (size - prevSize);
            cur->subFiles[p.back()]->size = size;
        }
        else {
            cur->cd += (size - prevSize);
            cur->cr += (size - prevSize);
            cur->subFiles[p.back()] = new File(false, p.back(), size);
        }
        return true;
    }
    bool deleteFile(string path) {
        vector<string> p = splitPath(path);
        LL size = 0;
        bool isFolder = false;
        // check if exists
        File *cur = root;
        for (int i = 0; i < p.size(); i++) {
            if (cur->subFiles.find(p[i]) == cur->subFiles.end()) {
                return true;
            }else {}

            if (i == p.size() - 1) {
                File * tmp = cur->subFiles[p[i]];
                cur->subFiles.erase(p[i]);
                cur = tmp;
            }
            else {
                cur = cur->subFiles[p[i]];
            }
        }
        if (cur->isFolder) {
            size = cur->cr;
            isFolder = true;
            cur->deleteSubFolder();
            delete cur;
        }
        else {
            size = cur->size;
            delete cur;
        }
        // update quota
        cur = root;
        for (int i = 0; i < p.size() - 1; i++) {
            cur->cr -= size;
            cur = cur->subFiles[p[i]];
        }
        cur->cr -= size;
        if (!isFolder) cur->cd -= size;
        return true;
    }
    bool changeQuota(string path, LL LD, LL LR) {
        vector<string> p = splitPath(path);
        File *cur = root;
        for (int i = 0; i < p.size(); i++) {
            if (cur->subFiles.find(p[i]) == cur->subFiles.end()) {
                return false;
            }
            else {
                cur = cur->subFiles[p[i]];
            }
        }
        if (!cur->isFolder) return false;
        if (LD != 0 && cur->cd > LD) {
            return false;
        }
        if (LR != 0 && cur->cr > LR) {
            return false;
        }
        cur->LD = LD;
        cur->LR = LR;
        return true;
    }
};

int N;

int main() {
    FS fs;
    cin >> N;
    while(N --) {
        char C;
        cin >> C;
        if (C == 'C') {
            string path;
            LL size;
            cin >> path >> size;
            bool res = fs.newFile(path, size);
            if (res) puts("Y");
            else puts("N");
        }
        else if (C == 'R') {
            string path;
            cin >> path;
            bool res = fs.deleteFile(path);
            if (res) puts("Y");
            else puts("N");
        }
        else {
            // C == 'Q
            string path;
            LL LD, LR;
            cin >> path >> LD >> LR;
            bool res = fs.changeQuota(path, LD, LR);
            if (res) puts("Y");
            else puts("N");
        }
    }
    return 0;
}