알고리즘
- 일반적인 다익스트라로 푸는데, 풀면서 이전에 어디서 왔는지를 기록한다.
- 다익스트라가 끝나고, 끝에서부터 왔던길을 되돌아가며 경로를 찾아낸다.
코드
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#include <iostream>
#include <queue>
#include <vector>
#include <cstring>
#define INF 2000000000000
typedef long long ll;
using namespace std;
int n, m, s, e, path[1001];
vector<int> p;
vector<pair<int, int>> to[1001];
priority_queue<pair<ll, int>> q;
ll cost[1001];
void dijkstra();
void checkPath();
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> m;
while (m--) {
int a, b, c;
cin >> a >> b >> c;
to[a].push_back({ b, c });
}
cin >> s >> e;
dijkstra();
checkPath();
cout << cost[e] << "\n";
cout << p.size() << "\n";
for (int i = p.size()-1; i >= 0; i--)
cout << p[i] << " ";
}
void dijkstra() {
for (int i = 0; i <= n; i++)
cost[i] = INF;
cost[s] = 0;
path[s] = -1;
q.push({ 0, s });
while (!q.empty()) {
ll c = -q.top().first;
int cur = q.top().second;
q.pop();
if (c > cost[cur])
continue;
for (int i = 0; i < to[cur].size(); i++) {
ll nc = c + to[cur][i].second;
int ncur = to[cur][i].first;
if (nc < cost[ncur]) {
cost[ncur] = nc;
path[ncur] = cur;
q.push({ -nc, ncur });
}
}
}
return;
}
void checkPath() {
int cur = e;
while (path[cur] != -1) {
p.push_back(cur);
cur = path[cur];
}
p.push_back(cur);
}