PAT 甲级 1030 Travel Plan

这题和1018很像，换了写法，先找最短路再dfs，写了下dijkstra算法，有点生疏。
快复试了，加油！

#include 
#include 
#include 
#include 
#include 
using namespace std;

struct edge
{
    bool flag = false;
    int l;
    int c;
};
edge map[505][505];
vector<int> pre[505];

int ans[505];
int tempans[505];
int num = 0;
int cost = -1;
int res = -1;
bool flag[505];


void init()
{
    memset(map, 0, sizeof(map));
    for (int i = 0; i < 505; i++)
    {
        pre[i].clear();
    }
}
void dijkstra(int s, int d, int n)
{
    int dis[505];
    memset(flag, 0, sizeof(flag));
    for (int i = 0; i < n; i++)
        dis[i] = 505 * 505;
    for (int i = 0; i < n; i++)
    {
        if (map[s][i].flag != 0)
        {
            dis[i] = map[s][i].l;
            pre[i].push_back(s);
        }
    }
    flag[s] = 1;
    while (!flag[d])
    {
        int min = 505 * 505;
        int p;
        for (int i = 0; i < n; i++)
        {
            if (min > dis[i]&&!flag[i])
            {
                min = dis[i];
                p = i;
            }
        }
        flag[p] = 1;
        for (int i = 0; i < n; i++)
        {
            if (!flag[i] && map[p][i].flag != 0)
            {
                if (dis[i] > map[p][i].l + dis[p])
                {
                    dis[i] = map[p][i].l + dis[p];
                    pre[i].clear();
                    pre[i].push_back(p);
                }
                else if (dis[i] == map[p][i].l + dis[p])
                {
                    pre[i].push_back(p);
                }
            }
        }
    }
    res = dis[d];
}
void dfs(int cnt,int c,int s, int d)
{
    if (s == d)
    {
        if (cost > c||cost == -1)
        {
            int temp = 1;
            ans[0] = s;
            for (int i = cnt-1; i >= 0; i--)
            {
                ans[temp++] = tempans[i];
            }
            num = temp;
            cost = c;
        }
    }
    else
    {
        for (int i = 0; i < pre[d].size(); i++)
        {
            int temp = pre[d][i];
            if (!flag[temp])
            {
                flag[temp] = 1;
                c += map[temp][d].c;
                tempans[cnt + 1] = temp;
                dfs(cnt + 1, c, s, temp);
                flag[temp] = 0;
                c -= map[temp][d].c;
            }
        }
    }
}
int main()
{
    int n, m, s, d;
    while (~scanf("%d%d%d%d", &n, &m, &s, &d))
    {
        init();
        int c1, c2, dis, c;
        for (int i = 0; i < m; i++)
        {
            scanf("%d%d%d%d", &c1, &c2, &dis, &c);
            map[c1][c2].l = map[c2][c1].l = dis;
            map[c1][c2].c = map[c2][c1].c = c;
            map[c1][c2].flag = 1;
            map[c2][c1].flag = 1;
        }
        dijkstra(s, d, n);


        memset(ans, 0, sizeof(ans));
        num = 0;
        cost = -1;
        memset(flag, 0, sizeof(flag));
        tempans[0] = d;
        dfs(0, 0, s, d);

        for (int i = 0; i < num; i++)
        {
            printf("%d ", ans[i]);
        }
        printf("%d %d\n", res, cost);
    }
    return 0;
}