私たちに示唆されたアルゴリズムを使用可能なコードに変換しようとするのに苦労しています。ここに出口とともに8つの座標（N、NE、NW、S、SE、SW、E、W）を持つDirection列挙型が与えられます。
これはヒント付きのアルゴリズムです。
getPathToExit(row, col):
if (row, col) is outside of the map:
return an empty list
else if (row, col) is an obstacle:
return an empty list
else if (row, col) is marked as visited or as deadend:
return an emtpy list
else if (row, col) is the exit:
//optional: mark exit as visited
return a list containing Direction.HERE
else:
//try to find a path from current square to exit:
mark current square as visited (that is, part of path)
for each neighbor of current square:
path = path from neighbor to exit
if path is not empty:
add (direction to neighbor) to start of path
return path
//after for loop: no path exists from this square to exit
mark current square as deadend
return empty list
これは私がしばらく取り組んできたコードです：
public java.util.ArrayList<Direction> getPathToExit(){
for (int x=0; x<map.length; x++){
for (int y=0; y<map[x].length; y++){
if (map[x][y]=='S'){
this.startRow=x;
this.startCol=y;
}
}
}
System.out.println("start "+startRow+", "+startCol);
return getPathToExit(this.startRow, this.startCol);
}
private java.util.ArrayList<Direction> getPathToExit(int row, int col){
Direction [] dirs = Direction.values();
ArrayList<Direction> path = new ArrayList<Direction>();
getPathToExit(row, col);
if (row < 0 || col < 0 || row > map.length || col > map[row].length){
return null;
}
else if (map[row][col] != ' '){
return null;
}
else if (map[row][col] == 'E'){
path.add(Direction.HERE);
return path;
}
else {
for (int x=0; x<dirs.length-1; x++){
int nextRow = row + dirs[x].getRowModifier();
int nextCol = col + dirs[x].getColModifier();
path = getPathToExit(nextRow, nextCol);
}
}
return path;
}
これは列挙型クラスです：
public enum Direction {
N, NE, E, SE, S, SW, W, NW, HERE;
/**
* Returns the X/column change on the screen that is associated with
* this direction: -1 for W, 0 for N/S, and +1 for E.
*/
public int getColModifier() {
int mod;
switch (this) {
case NW:
case W:
case SW:
mod = -1;
break;
case NE:
case E:
case SE:
mod = +1;
break;
default:
mod = 0;
break;
}
return mod;
}
/**
* Returns the Y/row change on the screen that is associated with
* this direction: -1 for N, 0 for E/W, and +1 for south.
*/
public int getRowModifier() {
int mod;
switch (this) {
case N:
case NE:
case NW:
mod = -1;
break;
case S:
case SE:
case SW:
mod = +1;
break;
default:
mod = 0;
break;
}
return mod;
}
/** As {@link #getColModifier()} */
public int getXModifier() {
return this.getColModifier();
}
/** As {@link #getRowModifier()} */
public int getYModifier() {
return this.getRowModifier();
}
/**
* Returns the direction that is the opposite of this one.
* For example, <code>Direction.NE.reverse() == Direction.SW</code>.
* (The opposite of HERE is still HERE though.)
*/
public Direction reverse() {
if (this == HERE) {
return this;
}else {
int reversed = (this.ordinal() + 4) % 8;
Direction[] dirs = Direction.values();
return dirs[reversed];
}
}
}
前もって感謝します。