spfa优化板子

用双端队列，当待加入元素小于队首元素时 加入队首， 否则 加入队尾

slf优化

                if(!vis[e.v])
                {
                    if(Q.empty()) Q.push_front(e.v);
                    else
                    {
                        if(d[e.v] < d[Q.front()]) Q.push_front(e.v);
                        else Q.push_back(e.v);
                    }
                    vis[e.v] = ;
                }

next从结构体中分离出来 用数组记录

using namespace std;
const int maxn = , INF = 0x7fffffff;
int n, m, s, t;
int head[maxn], nex[maxn << ], d[maxn], vis[maxn], cnt;

struct node
{
    int u, v, w;
}Node[maxn << ];

void add_(int u, int v, int w)
{
    Node[cnt].u = u;
    Node[cnt].v = v;
    Node[cnt].w = w;
    nex[cnt] = head[u];
    head[u] = cnt++;
}

void add(int u, int v, int w)
{
    add_(u, v, w);
    add_(v, u, w);
}

void spfa()
{
    deque<int> Q;
    for(int i = ; i < maxn; i++) d[i] = INF;
    Q.push_front(s);
    mem(vis, );
    d[s] = ;
    vis[s] = ;
    while(!Q.empty())
    {
        int u = Q.front(); Q.pop_front();
        vis[u] = ;
        for(int i = head[u]; i != -; i = nex[i])
        {
            int v = Node[i].v;
            if(d[v] > d[u] + Node[i].w)
            {
                d[v] = d[u] + Node[i].w;
                if(!vis[v])
                {
                    if(Q.empty()) Q.push_front(v);
                    else
                    {
                        if(d[v] < d[Q.front()]) Q.push_front(v);
                        else Q.push_back(v);
                    }
                    vis[v] = ;
                }
            }
        }
    }
}

int main()
{
    while(scanf("%d%d", &n, &m) && n + m)
    {
        mem(head, -);
        cnt = ;
        int u, v, w;
        for(int i = ; i < m; i++)
        {
            scanf("%d%d%d", &u, &v, &w);
            add(u, v, w);
        }
        s = , t = n;
        spfa();
        printf("%d\n", d[t]);
    }
    return ;
}