装满的油箱

算法：广搜变形(堆优化Dijkstra).

#include 
#include 
#include 
#include 

using namespace std;

typedef pair<int, int> PII;

const int N = 1010, C = 110, M = 20010;

int n, m;
int h[N], e[M], w[M], ne[M], idx;
int price[N];//每个地区的油价 
int dist[N][C];//存储距离
bool st[N][C];//判断是否走过
struct Ver
{
    int d, u, c;//分别表示当前点到起点的距离，当前点，当前剩余油量
    bool operator< (const Ver &W)const
    {
        return d > W.d;
    }
};

void add(int a, int b, int c)
{
    e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx ++ ;
}

int dijkstra(int start, int end, int cap)
{
    memset(dist, 0x3f, sizeof dist);
    memset(st, false, sizeof st);
    priority_queue heap;
    heap.push({0, start, 0});
    dist[start][0] = 0;

    while (heap.size())
    {
        auto t = heap.top(); heap.pop();

        if (t.u == end) return t.d;//如果当前点已经是终点，返回当前点到起点的距离

        if (st[t.u][t.c]) continue;
        st[t.u][t.c] = true;

        if (t.c < cap)//如果当前剩余油量小于车的油容量
        {
            if (dist[t.u][t.c + 1] > t.d + price[t.u])//当前距离可以进行更新
            {
                dist[t.u][t.c + 1] = t.d + price[t.u];
                heap.push({dist[t.u][t.c + 1], t.u, t.c + 1});//更新，存入堆
            }
        }

        for (int i = h[t.u]; ~i; i = ne[i])//第二种情况，枚举邻点
        {
            int j = e[i];
            if (t.c >= w[i])//当前剩余容量还可以到j点
            {
                if (dist[j][t.c - w[i]] > t.d)//并且距离也更短
                {
                    dist[j][t.c - w[i]] = t.d;//更新
                    heap.push({dist[j][t.c - w[i]], j, t.c - w[i]});
                }
            }
        }
    }

    return -1;
}

int main()
{
    scanf("%d%d", &n, &m);
    memset(h, -1, sizeof h);
    for (int i = 0; i < n; i ++ ) scanf("%d", &price[i]);
    for (int i = 0; i < m; i ++ )
    {
        int a, b, c;
        scanf("%d%d%d", &a, &b, &c);
        add(a, b, c), add(b, a, c);
    }

    int query;
    scanf("%d", &query);
    while (query -- )
    {
        int a, b, c;
        scanf("%d%d%d", &c, &a, &b);
        int t = dijkstra(a, b, c);
        if (t == -1) puts("impossible");
        else printf("%d\n", t);
    }

    return 0;
}

 

转载于:https://www.cnblogs.com/programyang/p/11335439.html