Dijkstra?

Problem - 20C - Codeforces

思路：

用dijkstra算法，在更新最短距离的时候在加一个存点的步骤，最后输出就可以了

p[i]是i的上一个点

完整代码：

#include <bits/stdc++.h>
#define int long long
#define PII std::pair<int,int>
const int N = 1e5 + 10;
int p[N];
signed main() {int n, m;int k = 0;std::cin >> n >> m;std::vector<std::vector<PII>> g(n + 1);std::vector<int> dist(n + 1, LLONG_MAX);std::vector<bool> vis(n + 1);dist[1] = 0;for (int i = 1; i <= m; i++) {int u, v, w;std::cin >> u >> v >> w;g[u].push_back({v, w});g[v].push_back({u, w});}std::priority_queue<PII, std::vector<PII >, std::greater<>> q;q.push({0, 1});//存dist和点while (!q.empty()) {auto node = q.top();q.pop();int cur = node.second;if (vis[cur] == true)continue;vis[cur] = true;for (int i = 0; i < g[cur].size(); i++) {int e = g[cur][i].first;int w = g[cur][i].second;if (dist[e] > dist[cur] + w) {p[e] = cur;//从cur走到edist[e] = dist[cur] + w;q.push({dist[e], e});}}}if(dist[n]==LLONG_MAX)std::cout<<-1;else {std::vector<int> a(n + 1);for (int i = n; i != 1; i = p[i]) {a[k++] = i;}std::cout << 1 << " ";for (int i = k - 1; i >= 0; i--) {std::cout << a[i] << " ";}}
//    std::cout<<dist[n];return 0;
}