PAT甲级 1175 Professional Ability Test（30）

有点复杂，考了两个知识点，拓扑排序+dijkstra，但是后三个测试点错误，目前不知道哪里错了><

等一个有缘人

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

struct Pair {
	int neighbor, score, voucher;
	Pair(int n, int s, int v): neighbor(n), score(s), voucher(v) {}
};

int N, M, T1, T2, S, D, K;
vector<vector<Pair>> neighbors;
vector<int> in; //入度 
vector<int> queries;

bool hasCircle();
vector<int>* dijkstra();

int main() {
	cin >> N >> M;
	neighbors.resize(N + 1, vector<Pair>()); //入度为0的点可能不止一个，增加一个哨兵点，只需一次dijkstra 
	in.resize(N + 1, 0);
	for (int i = 0; i < M; ++i) {
		cin >> T1 >> T2 >> S >> D;
		Pair p(T2 + 1, S, D);
		neighbors[T1 + 1].emplace_back(p);
		in[T2 + 1] += 1;
	}
	vector<int> oldin(in);
	cin >> K;
	queries.resize(K);
	for (int i = 0; i < K; ++i) {
		cin >> queries[i];
	}
	for (int i = 1; i <= N; ++i) {
		if (in[i] == 0) {
			++in[i];
			Pair p(i, 0, 0);
			neighbors[0].emplace_back(p); 
		}
	}
	if (hasCircle()) {
		cout << "Impossible." << endl;
		for (int& x: queries) {
			if (oldin[x + 1] == 0) {
				printf("You may take test %d directly.\n", x);
			} else {
				cout << "Error." << endl;
			}
		}
	} else {
		cout << "Okay." << endl;
		//求入度为0点的dijkstra
		vector<int>* pre = dijkstra();
		
		for (int& x: queries) {
			if (oldin[x + 1] == 0) {
				printf("You may take test %d directly.\n", x);
			} else {
				string s = "";
				s += to_string(x);
				while (true) {
					x = (*pre)[x + 1] - 1;
                    if (x == -1) {
                        break;
                    }
					s += ">-";
					s += to_string(x);
				}
				reverse(s.begin(), s.end());
				cout << s << endl;
			}
		}		
	}
	
	return 0;
}

bool hasCircle() {
	queue<int> tmpq;
	tmpq.push(0);
	vector<int> tmpin(in);
	int res = 0;
	while (!tmpq.empty()) {
		int i = tmpq.front();
		tmpq.pop();
		res++;
		for (auto& p: neighbors[i]) {
			int j = p.neighbor;
			if (--tmpin[j] == 0) {
				tmpq.push(j);
			}
		}
	}
	return res == N + 1 ? false : true;
}

vector<int>* dijkstra(){
	vector<int> scores(N + 1, INT_MAX);
	vector<int> vouchers(N + 1, 0);
	vector<int> pre(N + 1, -1);
	vector<int> visited(N + 1, 0);
	scores[0] = 0;
	while (true) {
		int u = -1, minScore = INT_MAX;
		for (int i = 0; i <= N; ++i) {
			if (visited[i] == 0 && scores[i] < minScore) {
				u = i;
				minScore = scores[i];
			}
		}
		if (u == -1) {
			break;
		}
		visited[u] = 1;
		for (auto& p: neighbors[u]) {
			if (visited[p.neighbor] == 0) {
				if (scores[p.neighbor] > scores[u] + p.score) {
					scores[p.neighbor] = scores[u] + p.score;
					vouchers[p.neighbor] = vouchers[u] + p.voucher;
					pre[p.neighbor] = u;
				} else if (scores[p.neighbor] == scores[u] + p.score) {
					if (vouchers[p.neighbor] < vouchers[u] + p.voucher) {
						vouchers[p.neighbor] = vouchers[u] + p.voucher;
						pre[p.neighbor] = u;
					}
				}
			}
		}
	}
	vector<int>* values = new vector<int>(pre);
	return values;
}