HDU 2757 Ocean Currents

HDU_2757

    由于边权只有0和1，可以用稍加变形的BFS，也可以直接用优先级队列，由于后者省事一些，所以就直接用优先级队列来写了，不过当然效率也会低一些。

#include<stdio.h>
#include<string.h>
#include<queue>
#define MAXD 1010
#define INF 0x3f3f3f3f
char b[MAXD];
int N, M, dis[MAXD][MAXD], g[MAXD][MAXD], sx, sy, tx, ty;
int dx[] = {-1, -1, 0, 1, 1, 1, 0, -1}, dy[] = {0, 1, 1, 1, 0, -1, -1, -1};
struct Point
{
    int x, y, dis;
    Point(){}
    Point(int _x, int _y, int _dis) : x(_x), y(_y), dis(_dis){}
    bool operator < (const Point &t) const
    {
        return dis > t.dis;    
    }
};
void init()
{
    int i, j;
    for(i = 1; i <= N; i ++)
    {
        scanf("%s", b + 1);
        for(j = 1; j <= M; j ++) g[i][j] = b[j] - '0';    
    }
}
inline int inside(int x, int y)
{
    return x >= 1 && x <= N && y >= 1 && y <= M;
}
void dij()
{
    int i, j, x, y, z;
    std::priority_queue <Point> q;
    for(i = 1; i <= N; i ++) for(j = 1; j <= M; j ++) dis[i][j] = INF;
    dis[sx][sy] = 0;
    q.push(Point(sx, sy, 0));
    while(!q.empty())
    {
        Point p = q.top();
        q.pop();
        if(p.x == tx && p.y == ty) break;
        for(i = 0; i < 8; i ++)
        {
            x = p.x + dx[i], y = p.y + dy[i];
            z = p.dis + 1 - (i == g[p.x][p.y]);
            if(inside(x, y) && z < dis[x][y])
                dis[x][y] = z, q.push(Point(x, y, z));
        }
    }
    printf("%d\n", dis[tx][ty]);
}
void solve()
{
    int i, n;
    scanf("%d", &n);
    for(i = 0; i < n; i ++)
    {
        scanf("%d%d%d%d", &sx, &sy, &tx, &ty);
        dij();    
    }
}
int main()
{
    while(scanf("%d%d", &N, &M) == 2)
    {
        init();
        solve();    
    }
    return 0;
}