我正在开发一个程序,我必须找到一个机器人在网格中的位置,它可以向前移动,并且可以将其面向北,南,东和西的方向更改,并已获得给定的命令顺序。那么,机器人的最终位置是什么。 禁止使用任何类型的条件分支(例如if / else,switch / case)。
示例-
网格-(100 * 500)
机器人的初始位置-(5,3)
可能的命令-
北北,
E-East,
W-West,
南南,
M向前移动
样本输入-{N,S,M.M,E,W,E,S,M,S,M}
我尝试使用Enum,但是我面临的问题是如何使用我通过命令获得的动态值调用Enum方法。
public class RobotMovesInGrid {
Scanner input = new Scanner(System.in);
String command=input.next();
int commLength = command.length();
static enum Command {
N{@Override public void execute(String g, String r){ System.out.println("do the N move here"); }},
E{@Override public void execute(String g, String r){ System.out.println("do the E move here"); }},
S{@Override public void execute(String g, String r){ System.out.println("do the S move here"); }},
W{@Override public void execute(String g, String r){ System.out.println("do the W move here"); }},
M{@Override public void execute(String g, String r){ System.out.println("do the M move here"); }};
public abstract void execute(String g, String r);
}
public void nextPosition() {
Command c1;
for(int i=0;i<commLength;i++) {
if (command.charAt(i)=='N'||command.charAt(i)=='E'|| command.charAt(i)=='S'|| command.charAt(i)=='W'||command.charAt(i)=='M')
c1= Command.M;// Here instead of M, I am trying to give dynamic commands but it is not taking it
System.out.println("Current position is"+c1);
}
}
}
有人可以建议我如何使用作为输入的命令调用Enum方法。
答案 0 :(得分:2)
这是另一种解决方案。
static enum Command {
N(-1,0),E(0,1),W(0,-1),S(1,0);
private int rowIncrement;
private int colIncrement;
private Command(int rowIncrement, int colIncrement)
{
this.rowIncrement = rowIncrement;
this.colIncrement = colIncrement;
}
public int getRowIncrement()
{
return rowIncrement;
}
public int getColIncrement()
{
return colIncrement;
}
}
这是命令评估的代码。
//input
String command = "NSMMEWESMSM";
int[] pos = new int[]{5,3};
int[] size = new int[]{100, 500};
char[] chars = command.toCharArray();
//replace M by the previous char, ie move in the same direction
for (int i = 0; i < chars.length; i++)
{
char dir = chars[i];
//this assumes that M cannot be the first char
if (dir == 'M')
{
dir = chars[i-1];
chars[i] = dir;
}
}
for (char dir : chars)
{
Command cmd = Command.valueOf(String.valueOf(dir));
pos[0] += cmd.rowIncrement;
//row is within the region
pos[0] = Math.min(Math.max(pos[0], 0), size[0] -1);
pos[1] += cmd.colIncrement;
//col is within the region
pos[1] = Math.min(Math.max(pos[1], 0), size[1] -1);
}
答案 1 :(得分:1)
最简单的方法是将输入char
转换为String
,然后调用枚举的valueOf(String)
方法来检索枚举,例如:
for(int i=0;i<commLength;i++) {
Command command = Command.valueOf(String.valueOf(command.charAt(i))
.toUpperCase());
if (command != null){
command.execute(...);
}
}
它可以工作,但我认为您的枚举值实际上没有任何意义。
您应该根据它们的含义重命名它们,使用包含映射字符的构造函数来丰富枚举类,并引入一个静态方法来检索与输入字符关联的枚举值:
static enum Command {
NORTH('N'){@Override public void execute(String g, String r){ System.out.println("do the N move here"); }},
EAST('E'){@Override public void execute(String g, String r){ System.out.println("do the E move here"); }},
SOUTH('S'){@Override public void execute(String g, String r){ System.out.println("do the S move here"); }},
WEST('W'){@Override public void execute(String g, String r){ System.out.println("do the W move here"); }},
MOVE_FORWARD('M'){@Override public void execute(String g, String r){ System.out.println("do the M move here"); }};
private char mappingChar;
Command (char mappingChar){
this.mappingChar = mappingChar;
}
public abstract void execute(String g, String r);
public static Optional<Command> getFrom(char mappingChar) {
for (Command command : values()) {
if (Character.toUpperCase(mappingChar)==command.mappingChar) {
return Optional.of(command);
}
}
return Optional.empty();
}
}
您现在可以动态检索枚举值并使用它:
for(int i=0;i<commLength;i++) {
Optional<Command> optCommand = Command.getFrom(command.charAt(i));
if (optCommand.isPresent()){
optCommand.get().execute(...)
}
// or alternatively
optCommand.ifPresent(c -> c.execute(...));
}
答案 2 :(得分:1)
一种实现方法是在内部类Map
中使用恒定的静态enum Commands
;它将String
与Commands
相关联。 Command.parse
在地图中查找命令。
import java.lang.String;
import java.util.Map;
import java.util.HashMap;
import java.util.Collections;
import java.util.function.Function;
import java.awt.Point;
import java.util.Scanner;
class Robot {
public static void main(String args[]) {
try(Scanner input = new Scanner(System.in)) {
input.useDelimiter(",\\s*|\n");
Robot r = new Robot();
while(input.hasNext()) {
try {
Command.parse(input.next().trim()).apply(r);
} catch(NullPointerException e) {
System.out.printf("Syntax error.\n");
} catch(RuntimeException e) {
System.out.printf("Can't go that way: %s.\n",
e.getMessage());
}
}
} catch(Exception e) {
System.err.printf("%s: %s.\n", e, e.getMessage());
}
}
Point x;
static Point dim;
Command last;
Robot() {
dim = new Point(100, 500);
x = new Point(5, 3);
}
enum Command {
N("N", "north", true, (r) -> new Point(r.x.x, r.x.y - 1)),
E("E", "east", true, (r) -> new Point(r.x.x + 1, r.x.y)),
S("S", "south", true, (r) -> new Point(r.x.x, r.x.y + 1)),
W("W", "west", true, (r) -> new Point(r.x.x - 1, r.x.y)),
M("M", "farther",false, (r) -> r.last != null ?r.last.go.apply(r):null);
private String command, name;
private boolean isDir;
private Function<Robot, Point> go;
private static final Map<String, Command> map;
/* Map for turning commands into Directions; mod->const map. */
static {
Map<String, Command> mod = new HashMap<>();
for(Command c : values()) mod.put(c.command, c);
map = Collections.unmodifiableMap(mod);
}
/** Called from definition of enum. */
private Command(final String command, final String name, boolean isDir,
final Function<Robot, Point> go) {
this.command = command;
this.name = name;
this.isDir = isDir;
this.go = go;
}
/** @param str A string representing the direction.
@return The command or null. */
public static Command parse(final String str) { return map.get(str); }
/** Applies this command to r. */
public void apply(Robot r) {
Point x = this.go.apply(r);
if(x == null)
throw new RuntimeException("don't have a direction");
if(x.x < 0 || x.x >= dim.x || x.y < 0 || x.y >= dim.y)
throw new RuntimeException("at the edge");
r.x = x;
if(this.isDir == true) r.last = this;
System.out.printf("Went %s to (%d, %d).\n", r.last.name, x.x, x.y);
}
/** @return The name of the direction. */
public String toString() { return name; }
}
}
它以EOF结尾。我发现这些有帮助,
答案 3 :(得分:0)
您可以使用Command.valueOf()
。
喜欢
c1 = Command.valueOf(command.toUpperCase());
这会将c1设置为与输入命令相对应的Command枚举值。
toUpperCase()
确保其与枚举名称相同。