文件系统 HDU-1413 HDU 2006-5 Programming Contest
https://vjudge.net/problem/HDU-1413
时间限制 1000ms 内存限制 32MB
这道题主要是直观上给出一个简单文件系统的树状印象，其实还是属于简单的数据结构题，做的话构造一棵根目录为根节点的有向树就可以。不外乎要注意一些细节上的处理。
我这里把文件和目录分开来处理了，对于这个问题而言是较为简单的做法，但是实际的文件系统实现可能是将目录也看作特殊的文件进行处理。而且文件表在磁盘上的存储方式并非简单的树，因为一个文件必须要考虑到充分利用磁盘空间，也就是一个文件可能存储在磁盘的不同位置上。这个树只是一个分区内文件的逻辑结构。鉴于现在还没学习操作系统课程，不好作深入探讨，只能就此打住。
1 #include<iostream> 2 #include<cstdio> 3 #include<set> 4 #include<map> 5 #include<string> 6 using namespace std; 7 struct folder 8 { 9 string name; 10 map<string, folder*> folders; 11 folder * parent; 12 set<string> files; 13 folder() 14 { 15 parent = NULL; 16 } 17 folder(string & fn, folder * pnt) 18 { 19 name = fn; 20 parent = pnt; 21 } 22 }; 23 folder * init() 24 { 25 return new folder; 26 } 27 folder * newfolder(folder * curfolder, string & fname) 28 { 29 if (fname == ".." || fname == "\") 30 return NULL; 31 map<string, folder*>::iterator it = curfolder->folders.find(fname); 32 if (it != curfolder->folders.end()) 33 return NULL; 34 folder * tmpfld = new folder(fname, curfolder); 35 curfolder->folders.insert(pair<string, folder *>(fname, tmpfld)); 36 return tmpfld; 37 } 38 folder * delfolder(folder * curfolder, string & fname) 39 { 40 map<string, folder*>::iterator it = curfolder->folders.find(fname); 41 if (it == curfolder->folders.end()) 42 return NULL; //not found 43 folder * fld = it->second; 44 if (!fld->files.empty() || !fld->folders.empty()) 45 return NULL; //has sub folders or files 46 delete it->second; 47 curfolder->folders.erase(it); 48 return curfolder; 49 } 50 folder * gotodir(folder * root, folder * cur, string &fname) 51 { 52 if (fname == "\") 53 return root; 54 if (fname == "..") 55 { 56 if (root == cur) 57 return root; 58 else 59 return cur->parent; 60 } 61 map<string, folder*>::iterator it = cur->folders.find(fname); 62 if (it == cur->folders.end()) 63 return NULL; //not found 64 else 65 return it->second; 66 } 67 int newfile(folder * curfolder, string & fname) 68 { 69 set<string>::iterator it = curfolder->files.find(fname); 70 if (it != curfolder->files.end()) 71 return -1; 72 curfolder->files.insert(fname); 73 return 0; 74 } 75 int delfile(folder * curfolder, string & fname) 76 { 77 set<string>::iterator it = curfolder->files.find(fname); 78 if (it == curfolder->files.end()) 79 return -1; 80 curfolder->files.erase(it); 81 return 0; 82 } 83 int main() 84 { 85 folder * root = init(); 86 folder * current = root; 87 string op; 88 while (cin >> op) 89 { 90 string fname; 91 cin >> fname; 92 if (op == "CD") 93 { 94 folder * tmpresult = gotodir(root, current, fname); 95 if (tmpresult == NULL) 96 cout << "no such directory" << endl; 97 else 98 { 99 cout << "success" << endl; 100 current = tmpresult; 101 } 102 } 103 else if (op == "MD") 104 { 105 if (newfolder(current, fname) == NULL) 106 cout << "directory already exist" << endl; 107 else 108 cout << "success" << endl; 109 } 110 else if (op == "RD") 111 { 112 if (delfolder(current, fname) == NULL) 113 cout << "can not delete the directory" << endl; 114 else 115 cout << "success" << endl; 116 } 117 else if (op == "CREATE") 118 { 119 if (newfile(current, fname) == -1) 120 cout << "file already exist" << endl; 121 else 122 cout << "success" << endl; 123 } 124 else if (op == "DELETE") 125 { 126 if (delfile(current, fname) == -1) 127 cout << "no such file" << endl; 128 else 129 cout << "success" << endl; 130 } 131 } 132 return 0; 133 }