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 }
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https://www.luogu.org/blog/Asurudo/solution-p1363
