poj2387

最短路

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <queue>
using namespace std;

#define V 1005
#define E 5005
#define inf 0x3f3f3f3f;

int cost[E], dist[V];
int e, pnt[E], nxt[E], head[V], prev[V], vis[V];
int n, m;

struct qnode
{
    int v, c;
    qnode(int vv = 0, int cc = 0) :
        v(vv), c(cc)
    {
    }
    bool operator <(const qnode &r) const
    {
        return c > r.c;
    }
};

void dijkstra(int n, const int src)
{
    qnode mv;
    int i, j, k, pre;
    priority_queue<qnode> que;
    vis[src] = 1;
    dist[src] = 0;
    que.push(qnode(src, 0));
    for (pre = src, i = 1; i < n; i++)
    {
        for (j = head[pre]; j != -1; j = nxt[j])
        {
            k = pnt[j];
            if (vis[k] == 0 && dist[pre] + cost[j] < dist[k])
            {
                dist[k] = dist[pre] + cost[j];
                que.push(qnode(pnt[j], dist[k]));
                prev[k] = pre;
            }
        }
        while (!que.empty() && vis[que.top().v] == 1)
            que.pop();
        if (que.empty())
            break;
        mv = que.top();
        que.pop();
        vis[pre = mv.v] = 1;
    }
}

inline void addedge(int u, int v, int c)
{
    pnt[e] = v;
    cost[e] = c;
    nxt[e] = head[u];
    head[u] = e++;
}

void init(int nv, int ne)
{
    int i, u, v;
    int c;
    e = 0;
    memset(head, -1, sizeof(head));
    memset(vis, 0, sizeof(vis));
    memset(prev, -1, sizeof(prev));
    for (i = 0; i < nv; i++)
        dist[i] = inf;
    for (i = 0; i < ne; ++i)
    {
        scanf("%d%d%d", &u, &v, &c);
        u--, v--;
        addedge(u, v, c);
        addedge(v, u, c);
    }
}

int main()
{
    //freopen("t.txt", "r", stdin);
    scanf("%d%d", &m, &n);
    init(n, m);
    dijkstra(n, 0);
    printf("%d\n", dist[n - 1]);
    return 0;
}