STL函数remove的用法：
Transforms the range [first,last) into a range with all the elements that compare equal to val removed,
and returns an iterator to the new end of that range.
#include <iostream>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>
#include <sstream>
#include <utility>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <ctime>
#include <cmath>
#include <cctype>
#define CLEAR(a, b) memset(a, b, sizeof(a))
#define IN() freopen("in.txt", "r", stdin)
#define OUT() freopen("out.txt", "w", stdout)
#define LL long long
#define maxn 10005
#define maxm 200005
#define mod 1000000007
#define INF 1000000007
#define eps 1e-5
#define PI 3.1415926535898
#define N 26
using namespace std;
//-------------------------CHC------------------------------//
vector<string> names;
map<string, int> id;
vector<int> before[maxn], after[maxn];
vector<int> installed;
int status[maxn];
int ID(string s) {
if (id.count(s)) return id[s];
names.push_back(s);
return id[s] = names.size() - 1;
}
void install(int u) {
for (int i = 0; i < before[u].size(); ++i)
install(before[u][i]);
if (!status[u]) {
status[u] = 2;
cout << " Installing " << names[u] << endl;
installed.push_back(u);
}
}
bool needed(int u) {
bool ret = false;
for (int i = 0; i < after[u].size(); ++i) {
if (status[after[u][i]]) ret = true;
}
return ret;
}
void remove(int u) {
status[u] = 0;
installed.erase(remove(installed.begin(), installed.end(), u), installed.end());
cout << " Removing " << names[u] << endl;
for (int i = 0; i < before[u].size(); ++i) {
int v = before[u][i];
if (status[v] == 2 && !needed(v))
remove(v);
}
}
int main() {
//IN(); OUT();
string in;
while (getline(cin, in)) {
cout << in << endl;
if (in[0] == 'E') break;
stringstream ss(in);
string op;
string name;
ss >> op;
if (op[0] == 'L') {
for (int i = 0; i < installed.size(); ++i)
cout << " " << names[installed[i]] << endl;
}
else {
ss >> name;
int u = ID(name);
if (op[0] == 'D') {
while (ss >> name) {
int v = ID(name);
before[u].push_back(v);
after[v].push_back(u);
}
}
else if (op[0] == 'I') {
if (status[u]) cout << " " << name << " is already installed.\n";
else {
install(u);
status[u] = 1;
}
}
else if (op[0] == 'R') {
if (status[u] == 0) cout << " " << name << " is not installed.\n";
else if (needed(u)) cout << " " << name << " is still needed.\n";
else remove(u);
}
}
}
return 0;
}
