算法實現系列第四章.啓發式搜索_A*搜索

..很鬱悶啓發式搜索和A*搜索.自己對照文檔寫了下..發現和之前學的有出入...算了先寫這個吧..等我回去翻翻筆記...如果有問題再來補充..明白的同學可以直接拍磚...

 

下面我們對這個圖進行..最短路徑的查

 

package algorithm;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map.Entry;
import java.util.Set;

/**
 * A* 搜索見得的java例子,也是啓發式搜索.和我映像裏有點出入...
 * 
 * @author ansj
 * 
 */
public class HeuristicSearching {
	public static void main(String[] args) {
		// 設置節點
		Node v1 = new Node("v1", 0);
		Node v2 = new Node("v2");
		Node v3 = new Node("v3");
		Node v4 = new Node("v4");
		Node v5 = new Node("v5");
		Node v6 = new Node("v6");

		// 設置關聯關係
		v1.hm.put(v2, 40);
		v1.hm.put(v3, 30);
		v1.hm.put(v4, 20);
		v1.hm.put(v5, 10);

		v2.hm.put(v6, 10);

		v3.hm.put(v2, 2);
		v3.hm.put(v6, 15);

		v4.hm.put(v2, 15);
		v4.hm.put(v3, 6);

		v5.hm.put(v4, 15);

		openNode(v1);

		System.out.println(v1);
		System.out.println(v2);
		System.out.println(v3);
		System.out.println(v4);
		System.out.println(v5);
		System.out.println(v6);

	}

	private static List<Node> open = new ArrayList<Node>();

	private static void openNode(Node from) {
		// TODO Auto-generated method stub

		Node temp = null;
		Integer pathWeight = null;
		if (from == null) {
			return;
		}
		for (Entry<Node, Integer> entry : from.hm.entrySet()) {
			temp = entry.getKey();
			// 如果此節點已經關閉.則忽略
			if (temp.close) {
				continue;
			}
			pathWeight = entry.getValue();
			if (temp.min > from.min + pathWeight) {
				temp.min = pathWeight + from.min;
			}
			open.add(temp);
		}
		// 每次關閉掉路徑最短的節點
		Node nodeMin = findAndRemoveMinNode();
		if(nodeMin!=null){
			openNode(nodeMin);
		}

	}

	private static Node findAndRemoveMinNode() {
		// TODO Auto-generated method stub
		Node node = null;
		for (int i = 0; i < open.size(); i++) {
			if (node == null) {
				node = open.get(i);
			} else if (open.get(i).min < node.min) {
				node = open.get(i);
			}
		}
		open.remove(node) ;
		return node;
	}

	// 節點對象
	private static class Node {
		// 節點名稱
		private String name;
		private boolean close = false;
		// 最短的路徑
		private int min = Integer.MAX_VALUE;
		// 可以到達的節點及其長度
		private HashMap<Node, Integer> hm = new HashMap<Node, Integer>();

		private Node(String name) {
			this.name = name;
		}

		private Node(String name, Integer pathWeight) {
			this.name = name;
			this.min = pathWeight;
		}

		public String toString() {
			return this.name + ":" + this.min;
		}
	}
}