2014 ACM/ICPC Asia Regional Guangzhou Online

Wang Xifeng's Little Plot http://acm.hdu.edu.cn/showproblem.php?pid=5024

预处理出每个点八个方向能走的最远距离，然后枚举起点，枚举方向，每走一步都要枚举左转和右转的情况，因为预处理好了，所以可以直接算出来。

 #include<cstdio>
 #include<algorithm>
 using namespace std;
 const int M=;
 char a[M][M];
 int n,dp[M][M][];
 int dx[]={-,-,,,,,,-};
 int dy[]={,,,,,-,-,-};
 bool inside(const int &x,const int &y){
     if(x>=&&x<n&&y>=&&y<n) return true;return false;
 }
 int getfar(int x,int y,int dir){
     int res=;
     while(true){
         x+=dx[dir];
         y+=dy[dir];
         if(!inside(x,y)||a[x][y]=='#') break;
         res++;
     }
     return res;
 }
 int turnleft(int dir){
     return (dir+)%;
 }
 int turnright(int dir){
     return (dir+)%;
 }
 int solve(int x,int y,int dir){
     int res=,step=,left=turnleft(dir),right=turnright(dir);
     while(true){
         x+=dx[dir];
         y+=dy[dir];
         if(!inside(x,y)||a[x][y]=='#') break;
         step++;
         res=max(res,step+dp[x][y][left]);
         res=max(res,step+dp[x][y][right]);
     }
     return res;
 }
 int main(){
     while(~scanf("%d",&n),n){
         for(int i=;i<n;i++){
             scanf("%s",a[i]);
         }
         for(int i=;i<n;i++){
             for(int j=;j<n;j++){
                 for(int k=;k<;k++){
                     if(a[i][j]=='#'){
                         dp[i][j][k]=-;
                     }
                     else{
                         dp[i][j][k]=getfar(i,j,k);
                     }
                 }
             }
         }
         int ans=;
         for(int i=;i<n;i++){
             for(int j=;j<n;j++){
                 if(a[i][j]=='.'){
                     for(int k=;k<;k++){
                         int now=solve(i,j,k);
                         ans=max(ans,now);
                     }
                 }
             }
         }
         printf("%d\n",ans);
     }
     return ;
 }

A Corrupt Mayor's Performance Art http://acm.hdu.edu.cn/showproblem.php?pid=5023

成段更新。

 #include<cstdio>
 #include<cstring>
 #define mt(a,b) memset(a,b,sizeof(a))
 #define lrrt int L,int R,int rt
 #define iall 1,n,1
 #define imid int mid=(L+R)>>1
 #define lson L,mid,rt<<1
 #define rson mid+1,R,rt<<1|1
 const int M=;
 struct T{
     int cover,lazy;
 }tree[M<<];
 void build(lrrt){
     tree[rt].cover=;
     tree[rt].lazy=;
     if(L==R) return ;
     imid;
     build(lson);
     build(rson);
 }
 void pushdown(int rt){
     if(tree[rt].lazy){
         tree[rt<<].lazy=tree[rt<<|].lazy=tree[rt<<].cover=tree[rt<<|].cover=tree[rt].lazy;
         tree[rt].lazy=;
     }
 }
 void pushup(int rt){
     tree[rt].cover=tree[rt<<].cover==tree[rt<<|].cover?tree[rt<<].cover:;
 }
 void update(int x,int y,int z,lrrt){
     if(x<=L&&R<=y){
         tree[rt].cover=tree[rt].lazy=z;
         return;
     }
     imid;
     pushdown(rt);
     if(mid>=x) update(x,y,z,lson);
     if(mid<y)  update(x,y,z,rson);
     pushup(rt);
 }
 bool vis[];
 void query(int x,int y,lrrt){
     if(L==R){
         vis[tree[rt].cover]=true;
         return ;
     }
     imid;
     if(x<=L&&R<=y){
         if(tree[rt].cover){
             vis[tree[rt].cover]=true;
             return ;
         }
         pushdown(rt);
         query(x,y,lson);
         query(x,y,rson);
         return ;
     }
     pushdown(rt);
     if(mid>=x) query(x,y,lson);
     if(mid<y)  query(x,y,rson);
 }
 int main(){
     int n,m,x,y,z;
     char op[];
     while(~scanf("%d%d",&n,&m),n|m){
         build(iall);
         while(m--){
             scanf("%s%d%d",op,&x,&y);
             if(op[]=='P'){
                 scanf("%d",&z);
                 update(x,y,z,iall);
             }
             else{
                 mt(vis,);
                 query(x,y,iall);
                 bool flag=false;
                 for(int i=;i<=;i++){
                     if(vis[i]){
                         if(flag) printf(" ");
                         printf("%d",i);
                         flag=true;
                     }
                 }
                 puts("");
             }
         }
     }
     return ;
 }

Saving Tang Monk http://acm.hdu.edu.cn/showproblem.php?pid=5025

集齐m把钥匙，就可以拯救唐僧，没集齐也可以从他身上踩过去，拿钥匙必须从小到大拿，蛇只要杀一次，所以要记录钥匙的状态和蛇是否被杀的状态。bfs。

 #include<cstdio>
 #include<cstring>
 #include<cctype>
 #include<queue>
 #define mt(a,b) memset(a,b,sizeof(a))
 using namespace std;
 const int M=;
 char a[M][M];
 int n,m;
 struct Snake{
     int x,y;
 }ts[];
 struct Q{
     int step,sta,x,y,snake;
     friend bool operator <(const Q &a,const Q &b){
         return a.step>b.step;
     }
 }now,pre;
 priority_queue<Q> q;
 bool vis[M][M][<<];
 int dx[]={,,,-};
 int dy[]={,-,,};
 int getkey(const int &psta,const int &x,const int &y){
     int ressta=psta;
     if(isdigit(a[x][y])){
         int his=a[x][y]-'';
         his=<<(his-);
         if(his-==psta){
             ressta|=his;
         }
     }
     return ressta;
 }
 int bfs(){
     int ls=;
     for(int i=;i<n;i++){
         for(int j=;j<n;j++){
             if(a[i][j]=='K'){
                 now.x=i;
                 now.y=j;
             }
             if(a[i][j]=='S'){
                 ts[ls].x=i;
                 ts[ls].y=j;
                 ls++;
             }
         }
     }
     now.snake=;
     now.sta=;
     now.step=;
     mt(vis,);
     vis[now.x][now.y][now.sta]=true;
     int End=(<<m)-;
     while(!q.empty()) q.pop();
     q.push(now);
     while(!q.empty()){
         pre=q.top();
         q.pop();
         if(a[pre.x][pre.y]=='T'&&pre.sta==End) return pre.step;
         for(int i=;i<;i++){
             int tx=pre.x+dx[i];
             int ty=pre.y+dy[i];
             if(tx>=&&tx<n&&ty>=&&ty<n&&a[tx][ty]!='#'){
                 now.sta=getkey(pre.sta,tx,ty);
                 if(!vis[tx][ty][now.sta]){
                     vis[tx][ty][now.sta]=true;
                     now.x=tx;
                     now.y=ty;
                     now.snake=pre.snake;
                     if(a[tx][ty]=='S'){
                         int id=;
                         for(int j=;j<ls;j++){
                             if(ts[j].x==tx&&ts[j].y==ty){
                                 id=j;
                                 break;
                             }
                         }
                         if((now.snake>>id)&){
                             now.step=pre.step+;
                         }
                         else{
                             now.snake|=(<<id);
                             now.step=pre.step+;
                         }
                     }
                     else{
                         now.step=pre.step+;
                     }
                     q.push(now);
                 }
             }
         }
     }
     return -;
 }
 int main(){
     while(~scanf("%d%d",&n,&m),n|m){
         for(int i=;i<n;i++){
             scanf("%s",a[i]);
         }
         int ans=bfs();
         if(ans==-) puts("impossible");
         else printf("%d\n",ans);
     }
     return ;
 }

end