【发布时间】：2017-05-21 03:54:53
【问题描述】：
我正在构建一个由单元格组成的 2D 网格游戏，玩家必须在其中放置标记并尝试包含（包围）对手的标记。现在每个单元格可以有 3 种状态：空、包含红色标记或包含蓝色标记。
所有可以形成“路径”的单元格都在一个列表中，沿着该路径我可以绘制经过单元格中心的线（多边形）。 还有一个包含令牌的列表，被包围的那个，
现在我想找到一种方法来“使”被包围的标记“无效”，以便路径计算可以忽略它
请看下面的例子：
- 蓝色标记首先被圈起来，它们不能脱离任何进一步的路径计算。
- 这是不允许的。先遏制，先赢。
以下所有代码均来自路径类：
class Path extends Stack<int[]>{
private Token[][] grid;
//a path shorter than min can not surround any cell
private static final int MIN_PATH_LEGTH = 3;
//a collection of cells that has been tested
private ArrayList<int[]>checked;
//represents the cell where the search starts from
int[] origin;
//represents the token of the origin
Token originToken;
private int rows;
private int cols;
//represents the path bounds: min/max row/col in path
private int minPathRow, maxPathRow, minPathCol, maxPathCol;
Path(Token[][] grid){
this.grid = grid;
rows = grid.length;
cols = grid[0].length;
}
//search for a path
boolean findPath(int[] origin) {
this.origin = origin;
int row = origin[0] , col = origin[1];
//represents the token of the origin
originToken = grid[row][col];
//initialize list of checked items
checked = new CellsList();
boolean found = findPath(row, col);
if(found) {
printPath();
} else {
System.out.println("No path found");
}
return found;
}
//recursive method to find path. a cell is represented by its row, col
//returns true when path was found
private boolean findPath(int row, int col) {
//check if cell has the same token as origin
if(grid[row][col] != originToken) {
return false;
}
int[] cell = new int[] {row, col};
//check if this cell was tested before to avoid checking again
if(checked.contains(cell)) {
return false;
}
//get cells neighbors
CellsList neighbors = getNeighbors(row, col);
//check if solution found. If path size > min and cell
//neighbors contain the origin it means that path was found
if((size() >= MIN_PATH_LEGTH) && neighbors.contains(origin) ) {
add(cell);
return true;
}
//add cell to checked
checked.add(cell);
//add cell to path
add(cell);
//if path was not found check cell neighbors
for(int[] neighbor : neighbors ) {
boolean found = findPath(neighbor[0],neighbor[1]);
if(found) {
return true;
}
}
//path not found
pop(); //remove last element from stack
return false;
}
//use for testing
private void printPath() {
System.out.print("Path : " );
for(int[] cell : this) {
System.out.print(Arrays.toString(cell));
}
System.out.println("");
List<int[]> containedCells = getContainedWithin();
System.out.print(containedCells.size() +" cell contained : " );
for(int[] cell : containedCells) {
System.out.print(Arrays.toString(cell));
}
System.out.println("");
}
CellsList getPath() {
CellsList cl = new CellsList();
cl.addAll(this);
return cl;
}
}
以下代码查找单元格的邻居（path.java）：
//return a list of all neighbors of cell row, col
private CellsList getNeighbors(int row, int col) {
CellsList neighbors = new CellsList();
for (int colNum = col - 1 ; colNum <= (col + 1) ; colNum +=1 ) {
for (int rowNum = row - 1 ; rowNum <= (row + 1) ; rowNum +=1 ) {
if(!((colNum == col) && (rowNum == row))) {
if(isWithinGrid (rowNum, colNum ) ) {
neighbors.add( new int[] {rowNum, colNum});
}
}
}
}
return neighbors;
}
private boolean isWithinGrid(int colNum, int rowNum) {
if((colNum < 0) || (rowNum <0) ) {
return false;
}
if((colNum >= cols) || (rowNum >= rows)) {
return false;
}
return true;
}
}
以下代码通过路径查找所有有界单元格（所有包含或包围的标记），并且它们的标记与路径的颜色相反：
List<int[]> getContainedWithin() {
//find path max and min X values, max and min Y values
minPathRow = grid[0].length; //set min to the largest possible value
maxPathCol = grid.length;
maxPathRow = 0; //set max to the largest possible value
maxPathCol = 0;
//find the actual min max x y values of the path
for (int[] cell : this) {
minPathRow = Math.min(minPathRow, cell[0]);
minPathCol = Math.min(minPathCol, cell[1]);
maxPathRow = Math.max(maxPathRow, cell[0]);
maxPathCol = Math.max(maxPathCol, cell[1]);
}
List<int[]> block = new ArrayList<>(25);
int[] cell = get(0);//get an arbitrary cell in the path
Token pathToken = grid[cell[0]][cell[1]]; //keep a reference to its token
//iterate over all cells within path x, y limits
for (int col = minPathCol; col < (maxPathCol); col++) {
for (int row = minPathRow; row < (maxPathRow); row++) {
//check cell color
Token token = grid[row][col];
if ((token == pathToken) || (token == Token.VIDE)) {
continue;
}
if (isWithinLoop(row,col)) {
block.add(new int[] {row, col});
}
}
}
return block;
}
//check if row, col represent a cell within path by checking if it has a
//path-cell to its left, right, top and bottom
private boolean isWithinLoop(int row, int col) {
if( isPathCellOnLeft(row, col)
&&
isPathCellOnRight(row, col)
&&
isPathCellOnTop(row, col)
&&
isPathCellOnBottom(row, col)
) {
return true;
}
return false;
}
}
如果你需要更多的元素，现在就告诉我，我会更新必要的。
【问题讨论】：
标签： java arraylist 2d path-finding