BFS(最短路) HDU 2612 Find a way

题目传送门

 /*
     BFS：和UVA_11624差不多，本题就是分别求两个点到KFC的最短路，然后相加求最小值
 */
 /************************************************
 Author        :Running_Time
 Created Time  :2015-8-4 19:36:36
 File Name     :HDOJ_2612.cpp
 ************************************************/

 #include <cstdio>
 #include <algorithm>
 #include <iostream>
 #include <sstream>
 #include <cstring>
 #include <cmath>
 #include <string>
 #include <vector>
 #include <queue>
 #include <deque>
 #include <stack>
 #include <list>
 #include <map>
 #include <set>
 #include <bitset>
 #include <cstdlib>
 #include <ctime>
 using namespace std;

 #define lson l, mid, rt << 1
 #define rson mid + 1, r, rt << 1 | 1
 typedef long long ll;
 const int MAXN = 2e2 + ;
 const int INF = 0x3f3f3f3f;
 const int MOD = 1e9 + ;
 char maze[MAXN][MAXN];
 bool vis[MAXN][MAXN];
 int step[MAXN][MAXN];
 int step2[MAXN][MAXN];
 int dx[] = {-, , , };
 int dy[] = {, , -, };
 int n, m;
 int sx, sy, ex, ey;

 bool judge_y(int x, int y)  {
     if (x <  || x > n || y <  || y > m || maze[x][y] == '#' || vis[x][y]) return false;
     return true;
 }

 bool judge_m(int x, int y)  {
     if (x <  || x > n || y <  || y > m || maze[x][y] == '#' || vis[x][y])  return false;
     return true;
 }

 void BFS_Y(void)    {
     memset (step, , sizeof (step));
     memset (vis, false, sizeof (vis));
     queue<pair<int, int> > Q;   Q.push (make_pair (sx, sy));
     vis[sx][sy] = true; step[sx][sy] = ;
     while (!Q.empty ()) {
         int x = Q.front ().first, y = Q.front ().second;    Q.pop ();
         for (int i=; i<; ++i) {
             int tx = x + dx[i], ty = y + dy[i];
             if (!judge_y (tx, ty))   continue;
             Q.push (make_pair (tx, ty));    vis[tx][ty] = true;
             step[tx][ty] = step[x][y] + ;
         }
     }
 }

 void BFS_M(void)    {
     memset (vis, false, sizeof (vis));
     memset (step2, , sizeof (step2));
     queue<pair<int, int> > Q;   Q.push (make_pair (ex, ey));
     vis[ex][ey] = true; step2[ex][ey] = ;
     while (!Q.empty ()) {
         int x = Q.front ().first, y = Q.front ().second;    Q.pop ();
         for (int i=; i<; ++i) {
             int tx = x + dx[i], ty = y + dy[i];
             if (!judge_m (tx, ty))  continue;
             step2[tx][ty] = step2[x][y] + ;
             Q.push (make_pair (tx, ty));    vis[tx][ty] = true;
         }
     }
 }

 int main(void)    {     //HDU 2612 Find a way
     while (scanf ("%d%d", &n, &m) == ) {
         for (int i=; i<=n; ++i)    {
             scanf ("%s", maze[i] + );
             for (int j=; j<=m; ++j)    {
                 if (maze[i][j] == 'Y')  sx = i, sy = j;
                 if (maze[i][j] == 'M')  ex = i, ey = j;
             }
         }
         BFS_Y ();   BFS_M ();
         int ans = INF;
         for (int i=; i<=n; ++i)    {
             for (int j=; j<=m; ++j)    {
                 if (maze[i][j] == '@' && vis[i][j])  {
                     ans = min (ans, step[i][j] + step2[i][j]);
                 }
             }
         }
         if (ans == INF) puts ("-1");
         else    printf ("%d\n", ans * );
     }

     return ;
 }