标签：des style blog http color os io strong
测试数据1:
5 5
BBBBB
B...B
BSE.B
B...B
BBBBB
测试数据2:
3 3
S..
...
..E
测试数据1：
Yes
0
测试数据2：
No
痛苦的bfs。。。我讨厌bfs。。。真TM难写
核心：对于当前位置，先判断下一个位置会不会冲出去，冲出去就没什么好做的了，
如果不会冲出去再判断是不是椅子
bfs的时候要传4个量：x,y（坐标），direction（方向），hit（撞击次数）
注意：1.由于范围很小，不需要像某些题解说的一次走一条直线，一步步慢慢挪也可以过（而且好像 也是0ms）
2.转向时候不能直接跨出去一步，应该是原地转向，然后入队直行，因为你不知道跨出去这一步是椅子还是出界，如果判断更麻烦
3.刚开始的时候需要将4个方向都入队
4.血的教训（见下）
x和y判断是否出界就是cin>>M>>N;x对应M，y对应N;
不要自作聪明调过来啊！！会死人啊！！
#include<iostream> #include<cstdlib> #include<cstdio> #include<algorithm> #include<cmath> #include<map> #include<ctime> #include<cstring> #define ll long long #define inf 0x7fffffff struct note { int x,y,dire,hitting; }; int N,M; note queue[2550]; int i,j,k,p,q,l,r,s,t,startx,starty,head,tail,left,right,use,tmp,sum,ans; const int movex[4]={-1,0,1,0}; const int movey[12]={0,1,0,-1}; char board[75][75]; bool b[75][75][5]={0}; bool flag; using namespace std; inline int read() { int x=0;char ch=getchar(); while(ch>‘9‘||ch<‘0‘)ch=getchar(); while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();} return x; } void readin() { cin>>M>>N; for (i=1;i<=M;i++) { for (j=1;j<=N;j++) { cin>>board[i][j]; if (board[i][j]==‘S‘) {startx=i;starty=j;} } } } //------------------------------------------------------------ void bfs() { while (head<=tail) { int xx,yy,direction,hit; xx=queue[head].x;yy=queue[head].y;direction=queue[head].dire;hit=queue[head].hitting; head++; if (board[xx][yy]==‘E‘) {ans=hit; flag=true; return;} if ( (xx+movex[direction]>0)&&(xx+movex[direction]<=M)&&(yy+movey[direction]>0)&&(yy+movey[direction]<=N) ) { if ( (board[xx+movex[direction]][yy+movey[direction]]==‘B‘) ) { int dir; dir=( (direction+1+4)%4 ); if ( (b[xx][yy][dir]==0)&&(xx<=M)&&(yy<=N)&&(xx>0)&&(yy>0) ) { tail++; queue[tail].x=xx;queue[tail].y=yy;queue[tail].dire=dir;queue[tail].hitting=hit+1; b[xx][yy][dir]=1; } dir=( (direction-1+4)%4 ); if ( (b[xx][yy][dir]==0)&&(xx<=M)&&(yy<=N)&&(xx>0)&&(yy>0) ) { tail++; queue[tail].x=xx;queue[tail].y=yy;queue[tail].dire=dir;queue[tail].hitting=hit+1; b[xx][yy][dir]=1; } } else { xx=xx+movex[direction];yy=yy+movey[direction]; if ( (b[xx][yy][direction]==0)&&(xx<=M)&&(yy<=N)&&(xx>0)&&(yy>0) ) { tail++; queue[tail].x=xx;queue[tail].y=yy;queue[tail].dire=direction;queue[tail].hitting=hit; b[xx][yy][direction]=1; } } } } } //------------------------------------------------------------ int main() { flag=false; readin(); head=1;tail=4; queue[1].x=startx;queue[1].y=starty;queue[1].dire=0;queue[1].hitting=0; b[startx][starty][0]=1; queue[2].x=startx;queue[2].y=starty;queue[2].dire=1;queue[2].hitting=0; b[startx][starty][1]=1; queue[3].x=startx;queue[3].y=starty;queue[3].dire=2;queue[3].hitting=0; b[startx][starty][2]=1; queue[4].x=startx;queue[4].y=starty;queue[4].dire=3;queue[4].hitting=0; b[startx][starty][3]=1; bfs(); if (flag==true) { cout<<"Yes"<<endl; cout<<ans<<endl; } else { cout<<"No"<<endl; } }
#include<iostream> #include<cstdlib> #include<cstdio> #include<algorithm> #include<cmath> #include<map> #include<ctime> #include<cstring> #define ll long long #define inf 0x7fffffff struct note { int x,y,dire,hitting; }; int N,M; note queue[2550]; int i,j,k,p,q,l,r,s,t,startx,starty,head,tail,left,right,use,tmp,sum,ans; const int movex[4]={-1,0,1,0}; const int movey[12]={0,1,0,-1}; char board[75][75]; bool b[75][75][5]={0}; bool flag; using namespace std; // 0 // 3 1 // 2 inline int read() { int x=0;char ch=getchar(); while(ch>‘9‘||ch<‘0‘)ch=getchar(); while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();} return x; } void readin() { cin>>M>>N; for (i=1;i<=M;i++) { for (j=1;j<=N;j++) { cin>>board[i][j]; if (board[i][j]==‘S‘) {startx=i;starty=j;} } } } //------------------------------------------------------------ void bfs() { /* 对于当前位置，先判断下一个位置会不会冲出去，冲出去就没什么好做的了， 如果不会冲出去再判断是不是椅子*/ while (head<=tail) { int xx,yy,direction,hit; xx=queue[head].x;yy=queue[head].y;direction=queue[head].dire;hit=queue[head].hitting; head++; if (board[xx][yy]==‘E‘) {ans=hit; flag=true; /*cout<<"到啦 喂 停车哇！！"<<endl;*/return;} /*Pending!cout<<"Pending:"<<queue[head-1].x<<‘ ‘<<queue[head-1].y<<‘ ‘<<queue[head-1].dire<<‘ ‘<<queue[head-1].hitting;*/ if ( (xx+movex[direction]>0)&&(xx+movex[direction]<=M)&&(yy+movey[direction]>0)&&(yy+movey[direction]<=N) ) //不会冲出去 { /*Pending!cout<<"不会冲出去 "; */ if ( (board[xx+movex[direction]][yy+movey[direction]]==‘B‘) ) //按着这个方向运行下去会撞车的情况 { /*Pending!cout<<"会撞车 "; */ int dir; dir=( (direction+1+4)%4 ); if ( (b[xx][yy][dir]==0)&&(xx<=M)&&(yy<=N)&&(xx>0)&&(yy>0) ) { /*Pending!cout<<"右拐 "; */ tail++; queue[tail].x=xx;queue[tail].y=yy;queue[tail].dire=dir;queue[tail].hitting=hit+1; b[xx][yy][dir]=1; } dir=( (direction-1+4)%4 ); if ( (b[xx][yy][dir]==0)&&(xx<=M)&&(yy<=N)&&(xx>0)&&(yy>0) ) { /*Pending!cout<<"左拐 "; */ tail++; queue[tail].x=xx;queue[tail].y=yy;queue[tail].dire=dir;queue[tail].hitting=hit+1; b[xx][yy][dir]=1; } } else //可以继续运行的情况 { /*Pending!cout<<"不会撞车 "; */ xx=xx+movex[direction];yy=yy+movey[direction]; if ( (b[xx][yy][direction]==0)&&(xx<=M)&&(yy<=N)&&(xx>0)&&(yy>0) ) { tail++; queue[tail].x=xx;queue[tail].y=yy;queue[tail].dire=direction;queue[tail].hitting=hit; b[xx][yy][direction]=1; } } } /*else Pending!cout<<"会冲出去 "; cout<<endl;*/ } } //------------------------------------------------------------ int main() { flag=false; readin(); head=1;tail=4; queue[1].x=startx;queue[1].y=starty;queue[1].dire=0;queue[1].hitting=0; b[startx][starty][0]=1; queue[2].x=startx;queue[2].y=starty;queue[2].dire=1;queue[2].hitting=0; b[startx][starty][1]=1; queue[3].x=startx;queue[3].y=starty;queue[3].dire=2;queue[3].hitting=0; b[startx][starty][2]=1; queue[4].x=startx;queue[4].y=starty;queue[4].dire=3;queue[4].hitting=0; b[startx][starty][3]=1; //for (i=1;i<=tail;i++) //cout<<queue[i].x<<‘ ‘<<queue[i].y<<‘ ‘<<queue[i].dire<<‘ ‘<<queue[i].hitting<<endl; //system("pause"); bfs(); if (flag==true) { cout<<"Yes"<<endl; cout<<ans<<endl; } else { cout<<"No"<<endl; } //for (i=1;i<=tail;i++) //cout<<queue[i].x<<‘ ‘<<queue[i].y<<‘ ‘<<queue[i].dire<<‘ ‘<<queue[i].hitting<<endl; }
const xi:array[1..4] of shortint=(1,-1,0,0); yi:array[1..4] of shortint=(0,0,1,-1); var d,i,j,m,n,x1,x2,y1,y2,k,ans:longint; a:array[0..51,0..51] of char; f:array[1..51,1..51,1..4] of longint; b:array[1..51,1..51,1..4] of boolean; procedure dfs(h,x,y,d:longint); var i,j,l,k,xx,yy:longint; begin //readln; x:=x+xi[d];y:=y+yi[d]; if (x>m) or (x=0) or (y>n) or (y=0) then exit; {for i:=1 to m do begin for j:=1 to n do write(f[i,j]:3); writeln; end; } if (a[x,y]<>‘B‘) then begin if (y=y2) and (x=x2) then begin if h<ans then ans:=h; exit; end; if (h>=f[x,y,d]) and not(b[x,y,d])then exit; if h<f[x,y,d] then f[x,y,d]:=h; b[x,y,d]:=false; while (a[x+xi[d],y+yi[d]]<>‘B‘) and (x+xi[d]<=m) and (x+xi[d]>0) and (y+yi[d]<=n) and (y+yi[d]>0) do begin x:=x+xi[d]; y:=y+yi[d]; if (h<f[x,y,d]) and (a[x,y]<>‘B‘) then f[x,y,d]:=h; if (y=y2) and (x=x2) then begin if h<ans then ans:=h; exit; end; b[x,y,d]:=false; end; end; if (a[x,y]<>‘B‘) then begin x:=x+xi[d];y:=y+yi[d]; end; if a[x,y]=‘B‘ then begin if d=1 then begin dec(x); if (a[x+xi[3],y+yi[3]]<>‘B‘) then dfs(h+1,x,y,3); if (a[x+xi[4],y+yi[4]]<>‘B‘) then dfs(h+1,x,y,4); end; if d=2 then begin inc(x); if (a[x+xi[3],y+yi[3]]<>‘B‘) then dfs(h+1,x,y,3); if (a[x+xi[4],y+yi[4]]<>‘B‘) then dfs(h+1,x,y,4); end; if d=3 then begin dec(y); if (a[x+xi[1],y+yi[1]]<>‘B‘) then dfs(h+1,x,y,1); if (a[x+xi[2],y+yi[2]]<>‘B‘) then dfs(h+1,x,y,2); end; if d=4 then begin inc(y); if (a[x+xi[1],y+yi[1]]<>‘B‘) then dfs(h+1,x,y,1); if (a[x+xi[2],y+yi[2]]<>‘B‘) then dfs(h+1,x,y,2); end; end; end; begin readln(m,n); for i:=1 to m do begin for j:=1 to n-1 do begin read(a[i,j]); if a[i,j]=‘S‘ then begin x1:=i;y1:=j; end; if a[i,j]=‘E‘ then begin x2:=i;y2:=j; end; end; readln(a[i,n]); if a[i,n]=‘S‘ then begin x1:=i;y1:=n; end; if a[i,n]=‘E‘ then begin x2:=i;y2:=n; end; end; for i:=1 to m+1 do for j:=1 to n+1 do for k:=1 to 4 do f[i,j,k]:=100; fillchar(b,sizeof(b),true); ans:=maxlongint; a[x1,y1]:=‘.‘; for d:=1 to 4 do dfs(0,x1,y1,d); if ans=maxlongint then writeln(‘No‘) else begin writeln(‘Yes‘); writeln(ans); end; end.
【bfs】【中等难度】tyvj P1234 - bench与奔驰,布布扣,bubuko.com
【bfs】【中等难度】tyvj P1234 - bench与奔驰
标签：des style blog http color os io strong
原文地址：http://www.cnblogs.com/seekdreamer/p/3917079.html
