HDU ACM 1242 Rescue(广搜BFS + 优先队列priority_queue)
http://acm.hdu.edu.cn/showproblem.php?pid=1242
题意:给出一幅图,由'#','.','a','x','r' 组成,
'#'表示墙 '.'表示路 'a'表示终点 'r'表示起点 'x'表示守卫
若要经过x你必须先用1时间打倒守卫,再用1事件走过1格
题目中说存在多个'r', 但我只找了一个却AC了
这题是赤裸裸的广搜题,直接用广搜做都是WA
改了一下方向向量的顺序就AC了.
View Code
1 #include <iostream> 2 #include <queue> 3 using namespace std; 4 const int MAX = 200 + 10; 5 const int INF = 0x3ffffff; 6 char map[MAX][MAX]; 7 int point[4][2]={0,1,0,-1,-1,0,1,0}; // 这里改成 int point[4][2]={0,1,0,-1,1,0,-1,0}; 就AC了 8 struct Node 9 { 10 int x; 11 int y; 12 int step; 13 }; 14 int n,m; 15 int mark; 16 int BFS(Node a,Node b) 17 { 18 queue <Node> q; 19 a.step = 0; 20 b.step = INF; 21 q.push(a); 22 map[a.x][a.y] = '#'; 23 while(!q.empty()) 24 { 25 Node mid; 26 mid = q.front(); 27 28 29 q.pop(); 30 if(mid.x == b.x && mid.y == b.y ) 31 { 32 return mid.step; 33 } 34 int i; 35 for(i=0;i<4;i++) 36 { 37 a.x = mid.x + point[i][0]; 38 a.y = mid.y + point[i][1]; 39 a.step = mid.step + 1; 40 if( a.x >= 1 && a.y >= 1 && a.x <=n && a.y <= m && map[a.x][a.y] != '#') 41 { 42 if(map[a.x][a.y] != '.' && map[a.x][a.y] != 'r' && map[a.x][a.y] != 'a') 43 { 44 a.step++; 45 q.push(a); 46 map[a.x][a.y] = '#'; 47 } 48 else 49 { 50 51 q.push(a); 52 map[a.x][a.y] = '#'; 53 } 54 } 55 } 56 } 57 return -1; 58 } 59 int main() 60 { 61 while(cin>>n>>m) 62 { 63 int i,j; 64 Node s,e; 65 memset(map,0,sizeof(map)); 66 for(i=1;i<=n;i++) 67 { 68 for(j=1;j<=m;j++) 69 { 70 cin>>map[i][j]; 71 if(map[i][j] == 'r') 72 { 73 s.x = i; 74 s.y = j; 75 } 76 if(map[i][j] == 'a') 77 { 78 e.x = i; 79 e.y = j; 80 } 81 } 82 } 83 mark = 1; 84 int ans = BFS(s,e); 85 86 if(ans == -1) 87 { 88 cout<<"Poor ANGEL has to stay in the prison all his life."<<endl; 89 } 90 else 91 { 92 cout<<ans<<endl; 93 } 94 } 95 }
这明显是坑爹的,于是把代码改成优先队列了.
View Code
1 #include <iostream> 2 #include <queue> 3 using namespace std; 4 const int MAX = 200 + 10; 5 const int INF = 0x3ffffff; 6 char map[MAX][MAX]; 7 int point[4][2]={0,1,0,-1,-1,0,1,0}; 8 struct Node 9 { 10 int x; 11 int y; 12 int step; 13 friend bool operator <(const Node a,const Node b) 14 { 15 return a.step > b.step; 16 } 17 }; 18 int n,m; 19 int mark; 20 void BFS(Node a,Node b) 21 { 22 priority_queue <Node> q; 23 a.step = 0; 24 b.step = INF; 25 q.push(a); 26 map[a.x][a.y] = '#'; 27 while(!q.empty()) 28 { 29 Node mid; 30 mid = q.top(); 31 if(mid.x == b.x && mid.y == b.y ) 32 { 33 cout<<mid.step<<endl; 34 mark = 0; 35 return ; 36 } 37 38 q.pop(); 39 int i; 40 for(i=0;i<4;i++) 41 { 42 a.x = mid.x + point[i][0]; 43 a.y = mid.y + point[i][1]; 44 a.step = mid.step + 1; 45 if( a.x >= 1 && a.y >= 1 && a.x <=n && a.y <= m && map[a.x][a.y] != '#') 46 { 47 if(map[a.x][a.y] == '.' || map[a.x][a.y] == 'r') 48 { 49 50 q.push(a); 51 map[a.x][a.y] = '#'; 52 } 53 else 54 { 55 a.step++; 56 q.push(a); 57 map[a.x][a.y] = '#'; 58 } 59 } 60 } 61 } 62 } 63 int main() 64 { 65 while(cin>>n>>m) 66 { 67 int i,j; 68 Node s,e; 69 memset(map,0,sizeof(map)); 70 for(i=1;i<=n;i++) 71 { 72 for(j=1;j<=m;j++) 73 { 74 cin>>map[i][j]; 75 if(map[i][j] == 'a') 76 { 77 s.x = i; 78 s.y = j; 79 } 80 if(map[i][j] == 'r') 81 { 82 e.x = i; 83 e.y = j; 84 } 85 } 86 } 87 mark = 1; 88 BFS(s,e); 89 if(mark) 90 { 91 cout<<"Poor ANGEL has to stay in the prison all his life."<<endl; 92 } 93 } 94 }
