Treasures and Vikings(两次搜索)

Treasures and Vikings

https://www.luogu.org/problemnew/show/P4668

题意翻译

你有一张藏宝图，藏宝图可视为

Translated by @Planet6174

题目描述

You have a treasure map that is arranged into a $\times MN×M grid. A grid square may be either sea or part of an island. In addition, the map shows the treasure and an enemy Viking ship that occupies one (sea) square. Finally, for convenience you have also drawn your own position.$

Now you must set up a fixed route to get the treasure. The route must start at your position, end at the treasure, and consist of a sequence of moves. In each move, you can go only to an (horizontally or vertically) adjacent square that is not part of an island. But beware: The Viking ship might follow you, using the same kind of moves! After each of your moves according to your route, the Viking ship may move or not. Your move and the Vikings’ reaction together is called a round.

After every round, the following checks are made:

If you are in line with the Viking ship (you are in the same vertical or horizontal line as the Viking ship with only sea between the Viking ship and you), you are dead.
If you aren’t dead and at the treasure-spot, you get the treasure.

Write a program that decides whether it is possible to set up a fixed route in advance such that you can get the treasure by following this route and will not get killed by the Vikings – no matter how the Viking ship moves.

输入输出格式

输入格式：

The first line of input contains two integers

输出格式：

The only line of the output must contain the string YES, if it is possible to set up a route to get the treasure, or NO otherwise.

输入输出样例

输入样例#1：

5 7
Y.....V
..I....
..IIIII
.......
...T...

输出样例#1：

YES

输入样例#2：

5 7
Y....V.
..I....
..IIIII
.......
...T...

输出样例#2：

NO

输入样例#3：

2 3
.YT
VII

输出样例#3：

NO

说明

Sample Explanation 1

The route is:go down for three times,go right for three times too,go down at last.

数据范围

对于 $50\%50% 的数据，1 ≤ N,M ≤ 200 1≤N,M≤200。$

对于所有数据，

  1 // luogu-judger-enable-o2
  2 #include<iostream>
  3 #include<cstdio>
  4 #include<cstring>
  5 #include<cmath>
  6 #include<string>
  7 #include<algorithm>
  8 #include<queue>
  9 #include<vector>
 10 using namespace std;
 11 
 12 char map[705][705];
 13 int book[705][705];
 14 int flag[705][705];
 15 int n,m;
 16 int yx,yy,vx,vy,tx,ty;
 17 struct sair{
 18     int x,y,step;
 19 };
 20 
 21 struct Step{
 22     int x,y,step,num,dir;
 23 };
 24 
 25 int dir[4][2]={0,1,0,-1,1,0,-1,0};
 26 
 27 void bfsV(){
 28     sair s,e;
 29     s.x=vx,s.y=vy,s.step=0;
 30     memset(book,-1,sizeof(book));
 31     queue<sair>Q;
 32     Q.push(s);
 33     flag[s.x][s.y]=1;
 34     book[s.x][s.y]=0;
 35     while(!Q.empty()){
 36         s=Q.front();
 37         Q.pop();
 38         int co=1;
 39         int tmp=s.y+co;
 40         while(tmp<m&&map[s.x][tmp]!='I'){
 41             if(book[s.x][tmp]==-1){
 42                 book[s.x][tmp]=s.step;
 43             }
 44             co++;
 45             tmp=s.y+co;
 46         }
 47         co=-1;
 48         tmp=s.y+co;
 49         while(tmp>=0&&map[s.x][tmp]!='I'){
 50             if(book[s.x][tmp]==-1){
 51                 book[s.x][tmp]=s.step;
 52             }
 53             co--;
 54             tmp=s.y+co;
 55         }
 56         co=1;
 57         tmp=s.x+co;
 58         while(tmp<n&&map[tmp][s.y]!='I'){
 59             if(book[tmp][s.y]==-1){
 60                 book[tmp][s.y]=s.step;
 61             }
 62             co++;
 63             tmp=s.x+co;
 64         }
 65         co=-1;
 66         tmp=s.x+co;
 67         while(tmp>=0&&map[tmp][s.y]!='I'){
 68             if(book[tmp][s.y]==-1){
 69                 book[tmp][s.y]=s.step;
 70             }
 71             co--;
 72             tmp=s.x+co;
 73         }
 74         for(int i=0;i<4;i++){
 75             e.x=s.x+dir[i][0];
 76             e.y=s.y+dir[i][1];
 77             if(e.x>=0&&e.x<n&&e.y>=0&&e.y<m&&map[e.x][e.y]!='I'&&!flag[e.x][e.y]){
 78                 flag[e.x][e.y]=1;
 79                 e.step=s.step+1;
 80                 Q.push(e);
 81             }
 82         }
 83     }
 84 }
 85 
 86 void bfsY(){
 87     sair s,e;
 88     queue<sair>Q;
 89     s.x=yx,s.y=yy,s.step=1;
 90     Q.push(s);
 91     memset(flag,0,sizeof(flag));
 92     while(!Q.empty()){
 93         s=Q.front();
 94         Q.pop();
 95         for(int i=0;i<4;i++){
 96             e.x=s.x+dir[i][0];
 97             e.y=s.y+dir[i][1];
 98             if(e.x>=0&&e.y<n&&e.y>=0&&e.y<m&&s.step<book[e.x][e.y]&&!flag[e.x][e.y]){
 99                 e.step=s.step+1;
100                 flag[e.x][e.y]=1;
101                 if(e.x==tx&&e.y==ty){
102                     puts("YES");
103                     return;
104                 }
105                 Q.push(e);
106             }
107         }
108     }
109     puts("NO");
110 }
111 
112 int main(){
113     scanf("%d %d%*c",&n,&m);
114     for(int i=0;i<n;i++){
115         scanf("%s%*c",map[i]);
116     }
117     for(int i=0;i<n;i++){
118         for(int j=0;j<m;j++){
119             if(map[i][j]=='Y'){
120                 yx=i,yy=j;
121             }
122             else if(map[i][j]=='V'){
123                 vx=i,vy=j;
124             }
125             else if(map[i][j]=='T'){
126                 tx=i,ty=j;
127             }
128         }
129     }
130     bfsV();
131  /*   for(int i=0;i<n;i++){
132         for(int j=0;j<m;j++){
133             cout<<book[i][j]<<" ";
134         }
135         cout<<endl;
136     }*/
137     bfsY();
138 }

View Code

posted on 2018-10-16 18:27 Fighting_sh 阅读(236) 评论(0) 编辑收藏举报

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