Uva - 506 - System Dependencies

模拟题，注意显示安装和隐式安装，显示安装的必须显示显示删除。把名字转化为整数维护。其他注意都注释了。输入稍微多一下，题目不是很麻烦。

AC代码：

#include <iostream>#include <cstdio>#include <cstdlib>#include <cctype>#include <cstring>#include <string>#include <sstream>#include <vector>#include <set>#include <map>#include <algorithm>#include <stack>#include <queue>#include <bitset> #include <cassert> using namespace std;const int maxn = 10000;int cnt = 0;map<string, int> name2id; // 把名字转化为整数，方便处理string name[maxn];vector<int> depend[maxn]; // 组件x所以来的组件列表vector<int> depended[maxn]; // 依赖于x的组件列表int status[maxn]; // 0表示组件x未安装，1表示显示安装，2表示隐式安装vector<int> installed; // 存放安装过的组件，安装过的就不要再安装了// 把名字转化为整数维护int ID(const string& item){if (!name2id.count(item)) {name[++cnt] = item;name2id[item] = cnt;}return name2id[item];}// 是否有组件依赖于itembool needed(int item){for (int i = 0; i < depended[item].size(); i++) {if (status[depended[item][i]]) {return true;}}return false;}// 安装item，如果有依赖项，递归的继续安装void install(int item, bool toplevel){if (!status[item]) {for (int i = 0; i < depend[item].size(); i++) {install(depend[item][i], false);}cout << "   Installing " << name[item] << endl;status[item] = toplevel ? 1 : 2;installed.push_back(item);}}// 判断是否能删除，如果能，删除之后递归的删除其他所依赖的组件void remove(int item, bool toplevel){if ((toplevel || status[item] == 2) && !needed(item)) {status[item] = 0;installed.erase(remove(installed.begin(), installed.end(), item), installed.end());cout << "   Removing " << name[item] << endl;for (int i = 0; i < depend[item].size(); i++) {remove(depend[item][i], false);}}}// 按照安装顺序输出void list(){for (int i = 0; i < installed.size(); i++) {cout << "   " << name[installed[i]] << endl;}}int main(){ios::sync_with_stdio(false);string line, cmd;memset(status, 0, sizeof(status));while (getline(cin, line)) {cout << line << endl;stringstream ss(line);ss >> cmd;if (cmd[0] == 'E') {break;}string item1, item2;if (cmd[0] == 'L') {list();}else {ss >> item1;int i1 = ID(item1);if (cmd[0] == 'D') {while (ss >> item2) {int i2 = ID(item2);depend[i1].push_back(i2);depended[i2].push_back(i1);}}else if (cmd[0] == 'I') {if (status[i1]) {cout << "   " << item1 << " is already installed.\n";}else {install(i1, true);}}else {if (!status[i1]) {cout << "   " << item1 << " is not installed.\n";}else if (needed(i1)) {cout << "   " << item1 << " is still needed.\n";}else {remove(i1, true);}}}}return 0;}