Java数据结构-栈（2）

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（注：日志类 Log 详见 http://blog.csdn.net/runninglion/article/details/46057643）

本示例程序主要用于实现利用栈走迷宫的功能，关于迷宫算法，请查看《数据结构》一书中的描述。

1. 位置描述类 Position，迷宫中的每个格子都是一个位置

package maze;public class Position {int x, y;public Position() {}public Position(int x, int y) {this.x = x;this.y = y;}public void setX(int x) {this.x = x;}public void setY(int y) {this.y = y;}public int getX() {return x;}public int getY() {return y;}}

2. 迷宫描述类 Maze，代表迷宫本身，它带有寻找可行路径的 traverse() 方法

package maze;import stack.LinkedStack;import stack.StackADT;public class Maze {private final int TRIED = 3;//private final int PATH = 7;private int [][] grid = {{1,1,1,0,0},{1,0,1,1,1},{0,1,0,0,1},};private StackADT<Position> pushNewPos(int x, int y,StackADT<Position> stack) {Position pos = new Position();pos.setX(x);pos.setY(y);if(isValid(pos.getX(), pos.getY())) {stack.push(pos);}return stack;}public boolean traverse() {boolean isDone = false;Position pos = new Position();StackADT<Position> stack = new LinkedStack<Position>();stack.push(pos);while(!isDone) {pos = stack.pop();if(null == pos) {isDone = false;break;} grid[pos.getX()][pos.getY()] = TRIED;if(pos.getX() == grid.length - 1&& pos.getY() == grid[0].length - 1) {isDone = true;} else {stack = pushNewPos(pos.getX(), pos.getY() - 1, stack);stack = pushNewPos(pos.getX(), pos.getY() + 1, stack);stack = pushNewPos(pos.getX() - 1, pos.getY(), stack);stack = pushNewPos(pos.getX() + 1, pos.getY(), stack);}}return isDone;}private boolean isValid(int row, int column) {boolean ret = false;if(row >= 0&& row < grid.length&& column >= 0&& column < grid[row].length) {if(1 == grid[row][column]) {return true;}}return ret;}public String toString() {String ret = "\n";for(int row = 0; row < grid.length; row++) {for(int col = 0; col < grid[row].length; col++) {ret += grid[row][col] + "";}ret += "\n";}return ret;}}

3. 辅助实现迷宫的栈的抽象数据类型 StackADT<T>

package stack;public interface StackADT<T> {public void push(T item);public T pop();public T peek(); // get the top item but not poppublic boolean isEmpty();public int size();public String toString();}

4. StackADT<T> 的一个具体实现

package stack;import util.Log;public class LinkedStack<T> implements StackADT<T> {private static final String LOG_TAG = LinkedStack.class.getName();private int mCount;private LinearNode<T> mTop;@Overridepublic void push(T item) {LinearNode<T> temp = new LinearNode<T>(item);temp.setNext(mTop);mTop = temp;mCount++;}@Overridepublic T pop() {if(isEmpty()) {Log.error(LOG_TAG, "pop()", "try to pop from an empty stack!");return null;}T ret = mTop.getElement();mTop = mTop.getNext();mCount--;return ret;}@Overridepublic T peek() {if(isEmpty()) {Log.error(LOG_TAG, "peek()", "try to peek from an empty stack!");return null;}return mTop.getElement();}@Overridepublic boolean isEmpty() {return 0 == mCount;}@Overridepublic int size() {return mCount;}/** * LinearNode class */public class LinearNode<T> {private T element;private LinearNode<T> next;public LinearNode() {next = null;element = null;}public LinearNode(T elem) {next = null;element = elem;}public LinearNode<T> getNext() {return next;}public void setNext(LinearNode<T> node) {next = node;}public T getElement() {return element;}public void setElement(T elem) {element = elem;}}}

5. 测试类 Main

package maze;import util.Log;public class Main {private static final String LOG_TAG = Main.class.getName();public static void main(String[] args) {Maze mazePath = new Maze();Log.info(LOG_TAG, "main()", mazePath.toString());if(mazePath.traverse()) {Log.info(LOG_TAG, "main()", "The maze was successfully traversed!");} else {Log.info(LOG_TAG, "main()", "There is no possible path!");}Log.info(LOG_TAG, "main()", mazePath.toString()); }}

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