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uva 10047 - The Monocycle bfs

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标签:uva

题目链接

A monocycle is a cycle that runs on one wheel and the one we will be considering is a bit more special. It has a solid wheel colored with five different colors as shown in the figure:

bubuko.com,布布扣

The colored segments make equal angles (72o) at the center. A monocyclist rides this cycle on an bubuko.com,布布扣grid of square tiles. The tiles have such size that moving forward from the center of one tile to that of the next one makes the wheel rotate exactly 72o around its own center. The effect is shown in the above figure. When the wheel is at the center of square 1, the mid-point of the periphery of its blue segment is in touch with the ground. But when the wheel moves forward to the center of the next square (square 2) the mid-point of its white segment touches the ground.

bubuko.com,布布扣

Some of the squares of the grid are blocked and hence the cyclist cannot move to them. The cyclist starts from some square and tries to move to a target square in minimum amount of time. From any square either he moves forward to the next square or he remains in the same square but turns 90o left or right. Each of these actions requires exactly 1 second to execute. He always starts his ride facing north and with the mid-point of the green segment of his wheel touching the ground. In the target square, too, the green segment must be touching the ground but he does not care about the direction he will be facing.

Before he starts his ride, please help him find out whether the destination is reachable and if so the minimum amount of time he will require to reach it.

Input 

The input may contain multiple test cases.

The first line of each test case contains two integers M and N (bubuko.com,布布扣bubuko.com,布布扣) giving the dimensions of the grid. Then follows the description of the grid in M lines of N characters each. The character `#‘ will indicate a blocked square, all other squares are free. The starting location of the cyclist is marked by `S‘ and the target is marked by `T‘. The input terminates with two zeros for M and N.

Output 

For each test case in the input first print the test case number on a separate line as shown in the sample output. If the target location can be reached by the cyclist print the minimum amount of time (in seconds) required to reach it exactly in the format shown in the sample output, otherwise, print ``destination not reachable".

Print a blank line between two successive test cases.

Sample Input 

1 3
S#T
10 10
#S.......#
#..#.##.##
#.##.##.##
.#....##.#
##.##..#.#
#..#.##...
#......##.
..##.##...
#.###...#.
#.....###T
0 0

Sample Output 

Case #1
destination not reachable
 
Case #2
minimum time = 49 sec



Miguel Revilla 
2000-12-26

题意:一自行车的轮子被分成5个扇区,涂了5种不同颜色。自行车每1秒要么骑到下一个格子,要么左转或者右转90。。一开始自行车面向北,颜色为绿,到达目标格时,必须触底颜色为绿,但朝向无限制。求到达目标格的最短时间。
分析:自从做了网赛那道,第一次了解了bfs的状态。。。这道题就是x,y坐标加上颜色,方向一共四个状态。。。
几个注意的地方:一个是那个四个方向必须按照顺时针顺序从北开始,另一个是最后组数据不能有多余空格。。。。。
/**
 * @author neko01
 */
//#pragma comment(linker, "/STACK:102400000,102400000")
#include <cstdio>
#include <cstring>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <queue>
#include <vector>
#include <cmath>
#include <set>
#include <map>
using namespace std;
typedef long long LL;
#define min3(a,b,c) min(a,min(b,c))
#define max3(a,b,c) max(a,max(b,c))
#define pb push_back
#define mp(a,b) make_pair(a,b)
#define clr(a) memset(a,0,sizeof a)
#define clr1(a) memset(a,-1,sizeof a)
#define dbg(a) printf("%d\n",a)
typedef pair<int,int> pp;
const double eps=1e-9;
const double pi=acos(-1.0);
const int INF=0x3f3f3f3f;
const LL inf=(((LL)1)<<61)+5;
char s[28][28];
bool vis[28][28][5][4];
struct node{
    int x,y,c,d,step;
    node(int x=0,int y=0,int c=0,int d=0,int step=0):x(x),y(y),c(c),d(d),step(step){}
};
int dir[4][2]={-1,0,0,1,1,0,0,-1};
int n,m,sx,sy;
bool immap(int x,int y)
{
    return x>=0&&y>=0&&x<n&&y<m&&s[x][y]!='#';
}
int bfs()
{
    clr(vis);
    queue<node>q;
    vis[sx][sy][0][0]=true;
    q.push(node(sx,sy,0,0,0));
    while(!q.empty())
    {
        node cur=q.front();
        q.pop();
        int x=cur.x,y=cur.y;
        if(s[x][y]=='T'&&cur.c==0) return cur.step;
        for(int i=0;i<4;i++)
        {
            if(i==cur.d)
            {
                int xx=x+dir[i][0];
                int yy=y+dir[i][1];
                int nowc=(cur.c+1)%5;
                if(immap(xx,yy)&&!vis[xx][yy][nowc][i])
                {
                    vis[xx][yy][nowc][i]=true;
                    q.push(node(xx,yy,nowc,i,cur.step+1));
                }
            }
            if(i==(cur.d-1+4)%4||i==(cur.d+1)%4)
            {
                if(!vis[x][y][cur.c][i])
                {
                    vis[x][y][cur.c][i]=true;
                    q.push(node(x,y,cur.c,i,cur.step+1));
                }
            }
        }
    }
    return -1;
}
int main()
{
    int cnt=0;
    while(~scanf("%d%d",&n,&m))
    {
        if(n==0&&m==0) break;
        for(int i=0;i<n;i++)
        {
            scanf("%s",s[i]);
            for(int j=0;j<m;j++)
            {
                if(s[i][j]=='S')
                    sx=i,sy=j;
            }
        }
        if(cnt!=0) puts("");
        int ans=bfs();
        printf("Case #%d\n",++cnt);
        if(ans==-1) puts("destination not reachable");
        else printf("minimum time = %d sec\n",ans);
    }
    return 0;
}






  Problem A: The Monocycle 

A monocycle is a cycle that runs on one wheel and the one we will be considering is a bit more special. It has a solid wheel colored with five different colors as shown in the figure:

bubuko.com,布布扣

The colored segments make equal angles (72o) at the center. A monocyclist rides this cycle on an bubuko.com,布布扣grid of square tiles. The tiles have such size that moving forward from the center of one tile to that of the next one makes the wheel rotate exactly 72o around its own center. The effect is shown in the above figure. When the wheel is at the center of square 1, the mid-point of the periphery of its blue segment is in touch with the ground. But when the wheel moves forward to the center of the next square (square 2) the mid-point of its white segment touches the ground.

bubuko.com,布布扣

Some of the squares of the grid are blocked and hence the cyclist cannot move to them. The cyclist starts from some square and tries to move to a target square in minimum amount of time. From any square either he moves forward to the next square or he remains in the same square but turns 90o left or right. Each of these actions requires exactly 1 second to execute. He always starts his ride facing north and with the mid-point of the green segment of his wheel touching the ground. In the target square, too, the green segment must be touching the ground but he does not care about the direction he will be facing.

Before he starts his ride, please help him find out whether the destination is reachable and if so the minimum amount of time he will require to reach it.

Input 

The input may contain multiple test cases.

The first line of each test case contains two integers M and N (bubuko.com,布布扣bubuko.com,布布扣) giving the dimensions of the grid. Then follows the description of the grid in M lines of N characters each. The character `#‘ will indicate a blocked square, all other squares are free. The starting location of the cyclist is marked by `S‘ and the target is marked by `T‘. The input terminates with two zeros for M and N.

Output 

For each test case in the input first print the test case number on a separate line as shown in the sample output. If the target location can be reached by the cyclist print the minimum amount of time (in seconds) required to reach it exactly in the format shown in the sample output, otherwise, print ``destination not reachable".

Print a blank line between two successive test cases.

Sample Input 

1 3
S#T
10 10
#S.......#
#..#.##.##
#.##.##.##
.#....##.#
##.##..#.#
#..#.##...
#......##.
..##.##...
#.###...#.
#.....###T
0 0

Sample Output 

Case #1
destination not reachable
 
Case #2
minimum time = 49 sec



Miguel Revilla 
2000-12-26

uva 10047 - The Monocycle bfs

标签:uva

原文地址:http://blog.csdn.net/neko01/article/details/40323771

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