- 时间:2016-02-24 15:49:41 星期三
- 题目编号:UVA 1601
- 题目大意:给定一个迷宫图,至多3个小写字母和等数目大写字符,求小写字母移动到大写字母的最少步数
- 迷宫宽度范围是4~16,字母个数是1~3,
- 分析:求最少步数,BFS,知道终点状态,可以用双向bfs优化
- 方法:BFS
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//单向bfs #include<iostream> #include<cstdio> #include<queue> #include<cstring> #include<algorithm> using namespace std; struct Node{ int t,now[3]; Node(int _t,int a = -1,int b = -1,int c = -1):t(_t){ now[0] = a;now[1] = b;now[2]= c; } }; struct Edge{ int to,nxt; }; Edge e[2000]; char mp[17][17]; int w,h,n,cnt,head[267]; int goal[3],start[3],vis[268][268][268]; int d[5][2] = {{0,0},{-1,0},{1,0},{0,1},{0,-1}}; void add(int u,int v){ e[cnt].to = v; e[cnt].nxt = head[u]; head[u] = cnt++; } void init(){ cnt = 0; memset(start,-1,sizeof(start)); memset(goal,-1,sizeof(goal)); memset(head,-1,sizeof(head)); for(int i = 0; i < h ;++i){ for(int j = 0;j < w;++j){ if(mp[i][j] == ‘#‘) continue; if(mp[i][j] >= ‘a‘ && mp[i][j] <= ‘c‘) start[ mp[i][j] - ‘a‘ ] = i*w + j; if(mp[i][j] >= ‘A‘ && mp[i][j] <= ‘C‘) goal[ mp[i][j] - ‘A‘ ] = i*w + j; for(int k = 0;k < 5;++k){ int ni = i + d[k][0],nj = j + d[k][1]; if(ni >= 0 && ni < h && nj >=0 && nj<w && mp[ni][nj]!=‘#‘) add(i*w+j,ni*w+nj); } } } } int bfs(){ queue<Node> q; memset(vis,0,sizeof(vis)); vis[start[0]+10][start[1]+10][start[2]+10] = 1; q.push(Node(0,start[0],start[1],start[2])); while(!q.empty()){ Node u = q.front();q.pop(); if(memcmp(u.now,goal,sizeof(goal)) == 0) return u.t; if(n==1){ for(int i=head[u.now[0]];i!=-1;i=e[i].nxt){ Node nxt=u; nxt.now[0]=e[i].to; if(vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10]) continue; vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10]=1; nxt.t=u.t+1; q.push(nxt); } }else if(n==2){ for(int i=head[u.now[0]];i!=-1;i=e[i].nxt){ Node nxt=u; nxt.now[0]=e[i].to; for(int j=head[u.now[1]];j!=-1;j=e[j].nxt){ nxt.now[1]=e[j].to; if(nxt.now[0]==nxt.now[1]) continue; if(nxt.now[0]==u.now[1]&&nxt.now[1]==u.now[0]) continue; if(vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10]) continue; vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10]=1; nxt.t=u.t+1; q.push(nxt); } } }else{ for(int i=head[u.now[0]];i!=-1;i=e[i].nxt){ Node nxt=u; nxt.now[0]=e[i].to; for(int j=head[u.now[1]];j!=-1;j=e[j].nxt){ nxt.now[1]=e[j].to; if(nxt.now[0]==nxt.now[1]) continue; if(nxt.now[0]==u.now[1]&&nxt.now[1]==u.now[0]) continue; for(int k=head[u.now[2]];k!=-1;k=e[k].nxt){ nxt.now[2]=e[k].to; if(nxt.now[2]==nxt.now[0]||nxt.now[2]==nxt.now[1]) continue; if(nxt.now[2]==u.now[0]&&nxt.now[0]==u.now[2]) continue; if(nxt.now[2]==u.now[1]&&nxt.now[1]==u.now[2]) continue; if(vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10]) continue; vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10]=1; nxt.t=u.t+1; q.push(nxt); } } } } } return -1; } int main(){ while(scanf("%d%d%d",&w,&h,&n) != EOF && (w || h || n)){ getchar(); for(int i = 0;i < h ; i++) gets(mp[i]); init(); printf("%d\n",bfs()); } return 0; } |
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//双向bfs #include<iostream> #include<cstdio> #include<queue> #include<cstring> #include<algorithm> using namespace std; struct Node{ int t,now[3]; Node(int _t,int a = -1,int b = -1,int c = -1):t(_t){ now[0] = a;now[1] = b;now[2]= c; } }; struct Edge{ int to,nxt; }; Edge e[2000]; char mp[17][17]; int w,h,n,cnt,head[267]; int goal[3],start[3],vis[268][268][268]; int d[5][2] = {{0,0},{-1,0},{1,0},{0,1},{0,-1}}; void add(int u,int v){ e[cnt].to = v; e[cnt].nxt = head[u]; head[u] = cnt++; } void init(){ cnt = 0; memset(start,-1,sizeof(start)); memset(goal,-1,sizeof(goal)); memset(head,-1,sizeof(head)); for(int i = 0; i < h ;++i){ for(int j = 0;j < w;++j){ if(mp[i][j] == ‘#‘) continue; if(mp[i][j] >= ‘a‘ && mp[i][j] <= ‘c‘) start[ mp[i][j] - ‘a‘ ] = i*w + j; if(mp[i][j] >= ‘A‘ && mp[i][j] <= ‘C‘) goal[ mp[i][j] - ‘A‘ ] = i*w + j; for(int k = 0;k < 5;++k){ int ni = i + d[k][0],nj = j + d[k][1]; if(ni >= 0 && ni < h && nj >=0 && nj<w && mp[ni][nj]!=‘#‘) add(i*w+j,ni*w+nj); } } } } int bfs(){ queue<Node> q[2]; memset(vis,0,sizeof(vis)); vis[start[0]+10][start[1]+10][start[2]+10] = 1; vis[goal[0]+10][goal[1]+10][goal[2]+10] = 2; q[0].push(Node(0,start[0],start[1],start[2])); q[1].push(Node(0,goal[0],goal[1],goal[2])); int cur = 1,visflg[2] = {1,2}; while(!q[0].empty() || !q[1].empty()){ cur ^= 1; int curct = q[cur].front().t; while(!q[cur].empty() && q[cur].front().t == curct){ Node u = q[cur].front();q[cur].pop(); if(n==1){ for(int i=head[u.now[0]];i!=-1;i=e[i].nxt){ Node nxt=u; nxt.now[0]=e[i].to; if(vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10] == visflg[cur^1]) return u.t + q[cur^1].front().t + 1; if(vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10] == visflg[cur]) continue; vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10]=visflg[cur]; nxt.t=u.t+1; q[cur].push(nxt); } }else if(n==2){ for(int i=head[u.now[0]];i!=-1;i=e[i].nxt){ Node nxt=u; nxt.now[0]=e[i].to; for(int j=head[u.now[1]];j!=-1;j=e[j].nxt){ nxt.now[1]=e[j].to; if(nxt.now[0]==nxt.now[1]) continue; if(nxt.now[0]==u.now[1]&&nxt.now[1]==u.now[0]) continue; if(vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10] == visflg[cur^1]) return u.t + q[cur^1].front().t + 1; if(vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10] == visflg[cur]) continue; vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10]=visflg[cur]; nxt.t=u.t+1; q[cur].push(nxt); } } }else{ for(int i=head[u.now[0]];i!=-1;i=e[i].nxt){ Node nxt=u; nxt.now[0]=e[i].to; for(int j=head[u.now[1]];j!=-1;j=e[j].nxt){ nxt.now[1]=e[j].to; if(nxt.now[0]==nxt.now[1]) continue; if(nxt.now[0]==u.now[1]&&nxt.now[1]==u.now[0]) continue; for(int k=head[u.now[2]];k!=-1;k=e[k].nxt){ nxt.now[2]=e[k].to; if(nxt.now[2]==nxt.now[0]||nxt.now[2]==nxt.now[1]) continue; if(nxt.now[2]==u.now[0]&&nxt.now[0]==u.now[2]) continue; if(nxt.now[2]==u.now[1]&&nxt.now[1]==u.now[2]) continue; if(vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10] == visflg[cur^1]) return u.t + q[cur^1].front().t + 1; if(vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10] == visflg[cur]) continue; vis[nxt.now[0]+10][nxt.now[1]+10][nxt.now[2]+10]=visflg[cur]; nxt.t=u.t+1; q[cur].push(nxt); } } } } } } return -1; } int main(){ while(scanf("%d%d%d",&w,&h,&n) != EOF && (w || h || n)){ getchar(); for(int i = 0;i < h ; i++) gets(mp[i]); init(); printf("%d\n",bfs()); } return 0; } |