P1363-幻象迷宫

 1 #include <bits/stdc++.h>
 2 #define _for(i,a,b) for(int i = (a);i < b;i ++)
 3 typedef long long ll;
 4 using namespace std;
 5 struct point
 6 {
 7     int x;
 8     int y;
 9     bool operator == (point b)
10     {
11         return this->x==b.x && this->y==b.y;
12     }
13 };
14 typedef pair<point,point> pir;
15 
16 inline ll read()
17 {
18     ll ans = 0;
19     char ch = getchar(), last = ' ';
20     while(!isdigit(ch)) last = ch, ch = getchar();
21     while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar();
22     if(last == '-') ans = -ans;
23     return ans;
24 }
25 inline void write(ll x)
26 {
27     if(x < 0) x = -x, putchar('-');
28     if(x >= 10) write(x / 10);
29     putchar(x % 10 + '0');
30 }
31 
32 int N,M;
33 char m[1504][1504];
34 bool vis[1504][1504];
35 point pre[1504][1504];
36 
37 point st;
38 int dx[] = {1,-1,0,0};
39 int dy[] = {0,0,1,-1};
40 bool bfs()
41 {
42     queue<pir> q;
43     q.push({st,st});
44     vis[st.x][st.y] = 1;
45     pre[st.x][st.y] = st;
46     while(!q.empty())
47     {
48         pir cur = q.front();q.pop();
49         point a = cur.first;
50         point b = cur.second;
51 
52         _for(i,0,4)
53         {
54             point ta;
55             ta.x = (a.x+dx[i]+N)%N;
56             ta.y = (a.y+dy[i]+M)%M;
57             point tb;
58             tb.x = b.x+dx[i];
59             tb.y = b.y+dy[i];
60 
61             if(vis[ta.x][ta.y] && !(tb==pre[ta.x][ta.y]))
62                 return true;
63 
64             if(vis[ta.x][ta.y] || m[ta.x][ta.y]=='#')
65                 continue;
66 
67             vis[ta.x][ta.y] = 1,pre[ta.x][ta.y] = tb;
68             q.push({ta,tb});
69         }
70     }
71     return false;
72 }
73 int main()
74 {
75     while(scanf("%d%d",&N,&M)!=EOF)
76     {
77         memset(m,0,sizeof(m));
78         memset(vis,0,sizeof(vis));
79         memset(pre,0,sizeof(pre));
80         _for(i,0,N)
81         _for(j,0,M)
82         {
83             cin >> m[i][j];
84             if(m[i][j]=='S')
85                 st.x = i,st.y = j,m[i][j] = '.';
86         }
87 
88         if(bfs())
89             printf("Yes\n");
90         else
91             printf("No\n");
92     }
93     return 0;
94 }