【鏈接】 我是鏈接,點我呀:)
【題意】

在這裏輸入題意

【題解】

記錄每個物品它的依賴有哪些,以及它被哪些東西依賴就可以了。
顯式安裝的東西不能被隱式刪除刪掉(就是remove item,然後刪除item的依賴的過程叫隱式刪除,而刪除item本身叫顯式刪除);
而只能被顯式刪除。
隱式安裝的依賴則可以被顯式或隱式刪除都行。
(顯示安裝指的是 install item,安裝item本身,而安裝item的依賴,都稱為是隱式的安裝)

寫個安裝和刪除的遞歸函數就好。
樣例的答案有誤。
remove browser那裏應該是先remove tcpip 後remove html.

【代碼】

/*
    1.Shoud it use long long ?
    2.Have you ever test several sample(at least therr) yourself?
    3.Can you promise that the solution is right? At least,the main ideal
    4.use the puts("") or putchar() or printf and such things?
    5.init the used array or any value?
    6.use error MAX_VALUE?
 

*/
#include <bits/stdc++.h>
using namespace std;

string s;
map <int,vector <int> > yilai,beiyilai;
map <int,int> status;
map <string,int> dic;
map <int,string> dic2;
vector <int> installed;
string ope;
int tot = 0;

void pd(string temp){
    if (dic[temp]==0) {
        dic[temp] = ++tot;
        dic2[tot] = temp;
    }
}

void
 
 ins(int id,bool highest){
    if (status[id]==0){
        if (yilai.find(id)!=yilai.end()){
            vector <int> v = yilai[id];
            int len = v.size();
            for (int i = 0;i < len;i++){
                int x = v[i];
                ins(x,0);               
            }
        }
        cout << "   Installing "<<dic2[id] << endl;
        installed.push_back(id);
        status[id] = (highest?1:2);
    }
}

bool need(int x){
    if (beiyilai.find(x)!=beiyilai.end()){
        vector <int> v = beiyilai[x];
        int len = v.size();
        for (int i = 0;i < len;i++){
            int x = v[i];
            if (status[x]) return true;
        }
    }
    return false;
}

void dele(int id,bool highest){
    if ( !need(id) && (highest || status[id]==2)){
        status[id] = 0;
        cout << "   Removing " << dic2[id] << endl;
        installed.erase(remove(installed.begin(),installed.end(),id),installed.end());
        if (yilai.find(id)!=yilai.end()){
            vector <int> v = yilai[id];
            int len = v.size();
            for (int i = 0;i < len;i++){
                int x = v[i];
                if (status[x]) dele(x,0);               
            }
        }
    }
}

int main(){
    #ifdef LOCAL_DEFINE
        freopen("F:\\c++source\\rush_in.txt", "r", stdin);
    #endif
    ios::sync_with_stdio(0),cin.tie(0);
    
    while (getline(cin,s)){
        yilai.clear(),beiyilai.clear(),     
        status.clear(),dic.clear();dic2.clear();
        installed.clear();
        while (s!="END"){
            cout << s << endl;
            stringstream ss(s);
            ss >> ope;
            if (ope=="INSTALL"){
                string x;
                ss >> x;
                pd(x);
                int y = dic[x]; 
                if (status[y]!=0)
                    cout <<"   "<<x<<" is already installed."<<endl;
                else
                    ins(y,1);
            }else if (ope=="REMOVE"){
                string x;
                ss >> x;
                pd(x);
                int y = dic[x];
                if (status[y]==0)
                    cout <<"   "<<x<<" is not installed."<<endl;
                else if (need(y))
                    cout <<"   "<<x<<" is still needed."<<endl;
                    else{
                        dele(y,1);
                    }
            }else if (ope=="LIST"){
                for (int x:installed){
                    cout <<"   "<<dic2[x]<<endl;
                }
            }else{
                //depend
                string x,y;int xx,yy;
                ss >> x;
                pd(x);xx = dic[x];
                while (ss>>y){
                    pd(y);yy = dic[y];
                    yilai[xx].push_back(yy);
                    beiyilai[yy].push_back(xx);
                }
            }
            getline(cin,s);
        }
        cout << s << endl;
    }

    return 0;
}

【例題 6-21 UVA - 506】System Dependencies