Dijkstra+SPFA 模板

Dijkstra

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 #include <algorithm>
 #include <cstdio>
 #include <cstring>
 #include <functional>
 #include <iostream>
 #include <queue>
 #include <vector>
 using namespace std;
 const int maxn =  + ;
 typedef pair<int, int> pii;
 struct Edge {
     int to, weight;
     Edge(int to, int weight) : to(to), weight(weight) {}
 };
 vector<vector<Edge>> G(MAXN);  //更快
 struct Dijkstra {              //打包在Dijkstra中
     int n, m;
     int dist[MAXN];
     int p[MAXN];
     Dijkstra(int n) : n(n) {
         for (int i = ; i <= n; i++) G[i].clear();
     }
     void AddEdge(int from, int to, int weight) {
         G[from].push_back(Edge(to, weight));  //保存from出发的边
     }
     void dijkstra(int s) {
         priority_queue<pii, vector<pii>, greater<pii>> Q;
         memset(dist, 0x7f, sizeof(dist));  //初始化为无穷大

         dist[s] = ;
         Q.push(pii(, s));  // pii (dist ,u)
         while (!Q.empty()) {
             pii P = Q.top();
             Q.pop();
             int u = P.second, d = P.first;
             Q.pop();
             if (dist[u] < d) continue;
             for (int i = ; i < G[u].size(); i++) {
                 Edge& e = G[u][i];
                 int v = e.to, w = e.weight;
                 if (dist[v] > dist[u] + w) {
                     dist[v] = dist[u] + w;
                     p[v] = u;  //记录到各点的最短路径
                     Q.push(pii(dist[v], v));
                 }
             }
         }
     }
 };
 int main() {
     int n, m, u, v, w;
     cin >> n >> m;  // n 点 , m 边
     Dijkstra d(n);
     for (int i = ; i < m; i++) {
         scanf("%d%d%d", &u, &v, &w);
         d.AddEdge(u, v, w);
         d.AddEdge(v, u, w);
     }
     d.dijkstra();              // 1点出发
     cout << d.dist[n] << endl;  //到n的最短路径

     vector<int> ans;  //到n点的最短路径
     for (int i = n; i != ; i = d.p[i]) ans.push_back(i);
     ans.push_back();
     for (int i = ans.size() - ; i >= ; i--) cout << ans[i] << ' ';

     return ;
 }

---

SPFA，向前星储存

 struct Edge{
     int from, to, w, next;
 }e[];
 int head[MAXN],vis[MAXN];
 int dist[MAXN];
 int n, m, tot;

 void add_edge(int i, int j, int w) {
     e[tot].from = i, e[tot].to = j, e[tot].w = w;
     e[tot].next = head[i]; head[i] = tot++;
 }

 void SPFA(int s){
     queue <int> q;
     for (int i = ; i <= n; i++)
         dist[i] = INF;
     memset(vis, false, sizeof(vis));
     q.push(s);
     dist[s] = ;
     while (!q.empty()){
         int u = q.front();
         q.pop();
         vis[u] = false;
         for (int i = head[u]; i != -; i = e[i].next){
             int v = e[i].to;
             if (dist[v] > dist[u] + e[i].w){
                 dist[v] = dist[u] + e[i].w;
                 if (!vis[v]){
                     vis[v] = true;
                     q.push(v);
                 }
             }
         }
     }
 }