Dijkstra+SPFA 模板

Dijkstra

引用自：点击打开链接

#include <algorithm>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iostream>
#include <queue>
#include <vector>
using namespace std;
const int maxn = 100000 + 5;
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 = 1; 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] = 0;
        Q.push(pii(0, 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 = 0; 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 = 0; i < m; i++) {
        scanf("%d%d%d", &u, &v, &w);
        d.AddEdge(u, v, w);
        d.AddEdge(v, u, w);
    }
    d.dijkstra(1);              // 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 != 1; i = d.p[i]) ans.push_back(i);
    ans.push_back(1);
    for (int i = ans.size() - 1; i >= 0; i--) cout << ans[i] << ' ';

    return 0;
}

---

SPFA，向前星储存

struct Edge{
    int from, to, w, next;
}e[1000001];
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 = 1; i <= n; i++)
        dist[i] = INF;
    memset(vis, false, sizeof(vis));
    q.push(s);
    dist[s] = 0;
    while (!q.empty()){
        int u = q.front();
        q.pop();
        vis[u] = false;
        for (int i = head[u]; i != -1; 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);
                }
            }
        }
    }
}