bfs

 1 #include<iostream>
 2 #include<queue>
 3 #include<bits/stdc++.h>
 4 using namespace std;
 5 int dir[4][2]={{1,0},{-1,0},{0,1},{0,-1}};
 6 char mat[105][105];
 7 int vis[105][105];
 8 int n,m,ans=-1;
 9 struct point
10 {
11     int x,y,step;
12     point(int xx,int yy,int ss)
13     {
14         x=xx;
15         y=yy;
16         step=ss;
17     }
18 };
19 void bfs(int x,int y,int step)
20 {
21     vis[x][y]=1;
22     queue<point> q;
23     q.push(point(x,y,step));
24     while(!q.empty())
25     {
26         point dp=q.front();
27         q.pop();
28         int dx=dp.x;
29         int dy=dp.y;
30         int dstep=dp.step;
31 
32         if(mat[dx][dy]==‘T‘)
33         {
34             ans=dstep;
35             return;
36         }
37 
38         for(int i=0;i<4;i++)
39         {
40             int nx=dx+dir[i][0];
41             int ny=dy+dir[i][1];
42             if(nx<0||ny<0||nx>=n||ny>=m||mat[nx][ny]==‘#‘||vis[nx][ny]) continue;
43             vis[nx][ny]=1;
44             q.push(point(nx,ny,dstep+1));
45         }
46     }
47 }
48 int main()
49 {
50     cin>>n>>m;
51     memset(vis,0,sizeof(vis));
52     int index=0;
53     for(int i=0;i<n;i++)
54     {
55         cin>>mat[i];
56     }
57     int start_x,start_y;
58     for(int i=0;i<n;i++)
59     {
60         for(int j=0;j<m;j++)
61         {
62             if(mat[i][j]==‘S‘)
63             {
64                 start_x=i;
65                 start_y=j;
66             }
67         }
68     }
69     bfs(start_x,start_y,0);
70     cout<<ans<<endl;
71     return 0;
72 }

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 int dir[4][2]={{1,0},{-1,0},{0,1},{0,-1}};
 4 //char mat[105][105];
 5 int vis[5005];
 6 int n,a,b;
 7 int ans;
 8 struct point
 9 {
10     int index,step;
11     point(int ii,int ss)
12     {
13         index=ii;
14         step=ss;
15     }
16 };
17 void bfs(int index,int step)
18 {
19     vis[index]=1;
20     queue<point> q;
21     q.push(point(index,step));
22     while(!q.empty())
23     {
24         point dp=q.front();
25         q.pop();
26         int di=dp.index;
27         int ds=dp.step;
28 
29         if(di==b)
30         {
31             ans=ds;
32             return;
33         }
34 
35         for(int i=0;i<3;i++)
36         {
37             int ni=di;
38             if(i==0) ni+=1;
39             else if(i==1) ni-=1;
40             else if(i==2) ni*=2;
41             if(ni>=0&&ni<=n&&!vis[ni])
42             {
43                 vis[ni]=1;
44                 q.push(point(ni,ds+1));
45             }
46         }
47     }
48 }
49 int main()
50 {
51     cin>>n>>a>>b;
52     memset(vis,0,sizeof(vis));
53     bfs(a,0);
54     cout<<ans<<endl;
55     return 0;
56 }

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 int dir[4][2]= {{1,0},{-1,0},{0,1},{0,-1}};
 4 int n,m;
 5 char mat[2005][2005];
 6 int vis[2005][2005][2];
 7 int ans;
 8 struct point
 9 {
10     int x,y,step;
11     point(int xx,int yy,int ss)
12     {
13         x=xx;
14         y=yy;
15         step=ss;
16     }
17 };
18 void dfs(point p)
19 {
20     queue<point> q;
21     q.push(p);
22     vis[p.x][p.y][0]=1;
23     vis[p.x][p.y][1]=0;
24     while(!q.empty())
25     {
26         point dp=q.front();
27         //cout<<"访问"<<"x:"<<dp.x<<"y:"<<dp.y<<"step:"<<dp.step<<endl;
28         q.pop();
29         if(mat[dp.x][dp.y]==‘P‘)
30         {
31             //cout<<"钥匙"<<"x:"<<dp.x<<"y:"<<dp.y<<endl;
32             vis[dp.x][dp.y][1]=1;
33         }
34         if(mat[dp.x][dp.y]==‘T‘&&vis[dp.x][dp.y][1])
35         {
36             //cout<<"终点:"<<dp.x<<" "<<dp.y<<endl;
37             ans=dp.step;
38             return;
39         }
40         for(int i=0; i<4; i++)
41         {
42             int nx=dp.x+dir[i][0];
43             int ny=dp.y+dir[i][1];
44             int nstep=dp.step+1;
45             if(nx>=0&&ny>=0&&nx<n&&ny<m&&mat[nx][ny]!=‘#‘)
46             {
47                 if(!vis[dp.x][dp.y][1])//没拿到钥匙
48                 {
49                     if(!vis[nx][ny][0])//没拿到钥匙时未访问过
50                     {
51                         vis[nx][ny][0]=1;
52                         q.push(point(nx,ny,nstep));
53                     }
54                 }
55                 else//拿到了钥匙
56                 {
57                     if(!vis[nx][ny][1])
58                     {
59                         vis[nx][ny][1]=1;
60                         q.push(point(nx,ny,nstep));
61                     }
62                 }
63             }
64         }
65     }
66 }
67 int main()
68 {
69     cin>>n>>m;
70     memset(vis,0,sizeof(vis));
71     for(int i=0; i<n; i++)
72     {
73         cin>>mat[i];
74     }
75     int start_x,start_y;
76     for(int i=0; i<n; i++)
77     {
78         for(int j=0; j<m; j++)
79         {
80             if(mat[i][j]==‘S‘)
81             {
82                 //cout<<"起点："<<i<<" "<<j<<endl;
83                 start_x=i;
84                 start_y=j;
85             }
86         }
87     }
88     dfs(point(start_x,start_y,0));
89     cout<<ans<<endl;
90     return 0;
91 }