HDU 1026 Ignatius and the Princess I（带路径的BFS）

http://acm.hdu.edu.cn/showproblem.php?pid=1026

题意:给出一个迷宫，求出到终点的最短时间路径。

这道题目在迷宫上有怪物，不同HP的怪物会损耗不同的时间，这个时候可以用优先队列，每次让时间最短的出队列。由于最后还需要输出路径，所以需要设置一个数组来保存路径。

#include<iostream>
#include<queue>
#include<cstring>
using namespace std;

const int maxn = 100 + 5;

struct node
{
    int x, y;
    int time;
    friend bool operator < ( node a, node b)   //重载<号
    {
        return b.time<a.time;
    }
};

char map[maxn][maxn];
int visited[maxn][maxn];
int path[maxn][maxn];
int  n, m;
int d[][2] = { { 1, 0 }, { -1, 0 }, { 0, 1 }, { 0, -1 } };

int bfs()
{    
    node q,now;
    priority_queue<node> p;
    q.x = 0;
    q.y = 0;
    q.time = 0;
    p.push(q);
    while (!p.empty())
    {
        q = p.top();
        p.pop();
        if (q.x == n - 1 && q.y == m - 1)  return q.time;
        for (int i = 0; i < 4; i++)
        {
            int xx = q.x + d[i][0];
            int yy = q.y + d[i][1];
            now.x = xx;
            now.y = yy;
            now.time = q.time;
            if (xx >= 0 && xx < n && yy >= 0 && yy < m && map[xx][yy]!='X' && !visited[xx][yy])
            {
                if (map[xx][yy] == '.')   now.time++;
                else now.time =now.time+ (map[xx][yy] - '0'+1);
                visited[xx][yy] = 1;
                path[xx][yy] = i + 1;     //记录路径
                p.push(now);
            }
        }
    }
    return -1;
}

int temp;

void print(int x, int y)
{
    int xx, yy;
    if (path[x][y] == 0)   return;
    xx = x - d[path[x][y] - 1][0];   //寻找第一个路径点
    yy = y - d[path[x][y] - 1][1];
    print(xx, yy);
    printf("%ds:(%d,%d)->(%d,%d)
", temp++, xx, yy, x, y);
    if (map[x][y] <= '9' && map[x][y] >= '0')
    {
        int m = map[x][y] - '0';
        while (m--)    printf("%ds:FIGHT AT (%d,%d)
", temp++, x, y);
    }
}

int main()
{
    while (cin >> n >> m && (n||m))
    {
        memset(visited, 0, sizeof(visited));
        memset(path, 0, sizeof(path));
        for (int i = 0; i < n;i++)
        for (int j = 0; j < m; j++)
            cin >> map[i][j];
        visited[0][0] = 1;
        int ans=bfs();
        if (ans == -1)  cout << "God please help our poor hero." << endl;
        else
        {
            cout << "It takes " << ans << " seconds to reach the target position, let me show you the way." << endl;
            temp = 1;
            print(n - 1,m - 1);
        }
        cout << "FINISH" << endl;
    }
    return 0;
}