【HDOJ】3085 Nightmare Ⅱ

双向BFS。注意，任何一个点出队后，首先需要考虑ghost。

 /* 3085 */
 #include <iostream>
 #include <queue>
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
 #include <cmath>
 using namespace std;

 #define MAXN 805

 typedef struct node_t {
     int x, y;
     node_t() {}
     node_t(int xx, int yy) {
         x = xx; y = yy;
     }
 } node_t;

 int n, m;
 node_t z[], beg0, beg1;
 char map[MAXN][MAXN];
 bool visit0[MAXN][MAXN];
 bool visit1[MAXN][MAXN];
 int dir[][] = {
     -,,,,,-,,
 };

 inline bool check(int x, int y) {
     return x< || x>=n || y< || y>=m;
 }

 inline bool meetZ(int x, int y, int t) {
     return abs(x-z[].x)+abs(y-z[].y)<=t+t || abs(x-z[].x)+abs(y-z[].y)<=t+t;
 }

 int bfs() {
     int size;
     int x, y, t = ;
     int i, j, k, r;
     node_t nd;
     queue<node_t> Q0;
     queue<node_t> Q1;

     memset(visit0, false, sizeof(visit0));
     memset(visit1, false, sizeof(visit1));
     visit0[beg0.x][beg0.y] = true;
     visit1[beg1.x][beg1.y] = true;
     Q0.push(beg0);
     Q1.push(beg1);

     while (!Q0.empty() || !Q1.empty()) {
         ++t;
         // Q0
         r = ;
         while (r--) {
             size = Q0.size();
             while (size--) {
                 nd = Q0.front();
                 Q0.pop();
                 if (meetZ(nd.x, nd.y, t))
                     continue;
                 for (i=; i<; ++i) {
                     x = nd.x + dir[i][];
                     y = nd.y + dir[i][];
                     if (check(x, y) || visit0[x][y])
                         continue;
                     if (map[x][y]=='X' || meetZ(x, y, t))
                         continue;
                     if (visit1[x][y])
                         return t;
                     visit0[x][y] = true;
                     Q0.push(node_t(x, y));
                 }
             }
         }
         // Q1
         size = Q1.size();
         while (size--) {
             nd = Q1.front();
             Q1.pop();
             if (meetZ(nd.x, nd.y, t))
                 continue;
             for (i=; i<; ++i) {
                 x = nd.x + dir[i][];
                 y = nd.y + dir[i][];
                 if (check(x, y) || visit1[x][y])
                     continue;
                 if (map[x][y]=='X' || meetZ(x, y, t))
                     continue;
                 if (visit0[x][y])
                     return t;
                 visit1[x][y] = true;
                 Q1.push(node_t(x, y));
             }
         }
     }

     return -;
 }

 int main() {
     int t;
     int i, j, k;

     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
         freopen("data.out", "w", stdout);
     #endif

     scanf("%d", &t);
     while (t--) {
         scanf("%d %d", &n, &m);
         k = ;
         for (i=; i<n; ++i) {
             scanf("%s", map[i]);
             for (j=; j<m; ++j) {
                 if (map[i][j] == 'Z') {
                     z[k].x = i;
                     z[k].y = j;
                     ++k;
                 } else if (map[i][j] == 'M') {
                     beg0.x = i;
                     beg0.y = j;
                 } else if (map[i][j] == 'G') {
                     beg1.x = i;
                     beg1.y = j;
                 }
             }
         }
         k = bfs();
         printf("%d\n", k);
     }

     return ;
 }