Spfa + 链式前向星（模板）

#include 
#include 
#include 
#include 
#include 
#include 
#define ll long long
#define inf 0x3f3f3f3f
#define pii pair
const int mod = 1e9+7;
const int maxn = 2e5+7;
using namespace std;
struct node {int to,w,next;} edge[maxn];
int head[maxn], cnt;
int dis[maxn], vis[maxn];
int n, m, s, t;
struct Spfa
{
    void init()
    {
        memset(head,-1,sizeof(head));
        memset(dis,0x3f,sizeof(dis));
        memset(vis,0,sizeof(vis));
        cnt = 0;
    }

    void add(int u,int v,int w)
    {
        edge[cnt].to = v;
        edge[cnt].w = w;
        edge[cnt].next = head[u];
        head[u] = cnt ++;
    }

    void spfa()
    {
        dis[s] = 0; vis[s] = 1;
        queue  Q; Q.push(s);
        while(!Q.empty())
        {
            int now = Q.front();
            Q.pop(); vis[now] = 0;    //从队列中弹出now , vis[now] 标记为未访问
            for(int i = head[now]; i != -1; i = edge[i].next)
            {
                int v = edge[i].to;
                if(dis[v] > dis[now] + edge[i].w)
                {
                    dis[v] = dis[now] + edge[i].w;
                    if(vis[v]) continue;    //如果访问过了(也就是 已经在队列中),就不用再push
                    vis[v] = 1; Q.push(v);
                }
            }
        }
    }
}sp;

int main()
{
    while(~scanf("%d%d",&n,&m) && n+m)
    {
        sp.init();
        for(int i = 0; i < m; i++)
        {
            int u, v, w;
            scanf("%d%d%d",&u, &v, &w);
            sp.add(u, v, w);
            sp.add(v, u, w);
        }
        s = 1, t = n; //s起点，t终点
        sp.spfa();
        printf("%d\n", dis[t]);
    }
}