HDU -2425(BFS)

题目链接： Hiking Trip

思路

本来以为求最短步数，美滋滋敲了一遍，后来看是求最小的花费。优先队列就是好使。

#include 
using namespace std;
char a[21][21];
int vis[21][21];
const int inf = 0x3f3f3f3f;
struct node{
   int x,y,time;
   bool operator<(const node &a)const
   {
       if(a.time != time)
        return a.time < time;
   }
};
int n,m;
int dir[4][2] = {{0,1},{0,-1},{1,0},{-1,0}};
map<char,int>M;
int ans;
int bfs(int x1,int y1,int x2,int y2)
{
    priority_queue<node>Q;
    vis[x1][y1] = 1;
    node A,B;
    A.x = x1;
    A.y = y1;
    A.time = 0;
    Q.push(A);
    while(!Q.empty())
    {
        A = Q.top();
        Q.pop();
        if(A.x == x2 && A.y == y2)
           return A.time;
        for(int i = 0; i < 4; ++i)
        {
            int xx = A.x + dir[i][0];
            int yy = A.y + dir[i][1];
            if(a[xx][yy] == '@' || xx < 0 || xx >= n || yy < 0 || yy >= m || vis[xx][yy])
                continue;
            vis[xx][yy] = 1;
            B.x = xx;
            B.y = yy;
            B.time = A.time + M[a[xx][yy]];
            Q.push(B);
        }
    }
    return -1;
}
int main()
{
    int VP,VS,VT,caser = 1;
    int x1,y1,x2,y2;
    ans = inf;
    while(cin >> n >> m)
    {
        M.clear();
        memset(vis,0,sizeof(vis));
    cin >> VP >> VS >> VT;
    M['#'] = VP;
    M['T'] = VT;
    M['.'] = VS;
    for(int i = 0; i < n; ++i)
    {
        for(int j = 0; j < m; ++j)
        {
            cin >> a[i][j];
        }
    }
    cin >> x1 >> y1 >> x2 >> y2;
    cout << "Case " << caser++ << ": " ;
    int c = bfs(x1,y1,x2,y2);
    if(c == -1)
        cout << "-1" << endl;
    else
        cout << c << endl;
    }

}