poj2394

最短路，有重边

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

#define INF 0x3f3f3f3f
#define N 505

int path[N], vis[N];
int n, m, c, p;
int lowcost[N];
int cost[N][N];
int cow[N];
int ans[N];

void Dijkstra()
{
    int i, j, min;
    memset(vis, 0, sizeof(vis));
    int beg = 0;
    vis[beg] = 1;
    for (i = 0; i < n; i++)
    {
        lowcost[i] = cost[beg][i];
        path[i] = beg;
    }
    lowcost[beg] = 0;
    path[beg] = -1;
    int pre = beg;
    for (i = 1; i < n; i++)
    {
        min = INF;
        for (j =0; j < n; j++)
            if (vis[j] == 0 && lowcost[pre] + cost[pre][j] <lowcost[j])
            {
                lowcost[j] = lowcost[pre] + cost[pre][j];
                path[j] = pre;
            }
        for (j = 0; j < n; j++)
            if (vis[j] == 0 && lowcost[j] < min)
            {
                min = lowcost[j];
                pre = j;
            }
        vis[pre] = 1;
    }
}

int main()
{
    //freopen("t.txt", "r", stdin);
    scanf("%d%d%d%d", &n, &m, &c, &p);
    for (int i = 0; i < n; i++)
        for (int j = 0; j < n; j++)
            cost[i][j] = INF;
    for (int i = 0; i < n; i++)
        cost[i][i] = 0;
    for (int i = 0; i < m; i++)
    {
        int a, b, x;
        scanf("%d%d%d", &a, &b, &x);
        a--;
        b--;
        cost[a][b] = cost[b][a] = min(x, cost[a][b]);
    }
    for (int i = 0; i < c; i++)
        scanf("%d", &cow[i]);
    Dijkstra();
    int tot = 0;
    for (int i = 0; i < c; i++)
        if (lowcost[cow[i] - 1] <= p)
            ans[tot++] = i;
    sort(ans, ans + tot);
    printf("%d\n", tot);
    for (int i = 0; i < tot; i++)
        printf("%d\n", ans[i] + 1);
    return 0;
}