Dijkstra求最短路径

package org.test;import java.util.Collections;import java.util.HashMap;import java.util.LinkedHashMap;import java.util.LinkedList;import java.util.Map;import java.util.Map.Entry;import java.util.Optional;import java.util.Random;public class MyDijkstra {private final int m_max = Integer.MAX_VALUE;private int m_total;private int[][] m_matirx; private int[] m_mark; private Map<String,Map<String,Integer>> m_line;private Map<String,Integer> m_nodesPos = new HashMap<String,Integer>();/** *  * @param nodes 所有的顶点 * @param line 所有直接相连顶点间的距离(双向) */public MyDijkstra(String[] nodes,Map<String,Map<String,Integer>> line){this.m_total = nodes.length;m_matirx = new int[this.m_total][this.m_total];m_mark = new int[m_total];for(int i = 0; i < m_total; i++){for(int j = 0; j < m_total; j++){if (i == j){m_matirx[i][j] = 0;}else{m_matirx[i][j] = m_max;}}m_nodesPos.put(nodes[i], i);}line.forEach((id1,lines)->{lines.forEach((id2,length)->{m_matirx[m_nodesPos.get(id1)][m_nodesPos.get(id2)] = length;});});m_line = line;}private void printMatirx(){for (int i = 0; i < m_total; i++){for(int j = 0; j < m_total; j++){if (this.m_matirx[i][j] == this.m_max){System.out.print(" ∞ " + "-");}else{System.out.print(String.format("%03d", this.m_matirx[i][j]) + "-");}}System.out.print("\n");}}private String getShortestDirectlyConnected(String s,String e) throws Exception{int minLength = this.m_max;String ret = null;for(String p1 : m_line.keySet()){if (p1.equals(e)){Map<String,Integer> line1 = m_line.get(p1);for(String p2 : line1.keySet()){int length = this.m_matirx[this.m_nodesPos.get(s)][this.m_nodesPos.get(p2)] + this.m_line.get(e).get(p2);if (length < minLength){minLength = length;ret = p2;}}return ret;}}throw new Exception("imposiable");}private LinkedList<String> getShortestRoadLine(String s,String e){LinkedList<String> ret = new LinkedList<String>();if (s.equals(e)){return ret;}String end = e;ret.add(e);try{while(true){String mid = getShortestDirectlyConnected(s,end);ret.add(mid);//System.out.println("------->" + s + "," + end + "," + mid);if (mid.equals(s)){Collections.reverse(ret);return ret;}end = mid;}}catch (Exception ex){return ret;}}public Optional <LinkedList<String>> getShortestRoad(String str,String etr){int s = this.m_nodesPos.get(str);int e = this.m_nodesPos.get(etr);int [] dis = new int[m_total];for(int i = 0; i < this.m_total; i++){m_mark[i] = 0;dis[i] = this.m_matirx[s][i];}dis[s] = 0;this.m_mark[s] = 1;int min = -1;int k = -1;for(int i = 0; i < this.m_total; i++){min = this.m_max;for(int j = 0; j < this.m_total; j++){if (this.m_mark[j] == 0 && dis[j] < min){min = dis[j];k = j;}}//取出了下一个距离s路径最近的点,可能s直接是孤立点if (k == -1){return Optional.ofNullable(null);}this.m_mark[k] = 1;//修正以前的结果（j到原点的距离可能随着新的k距离的更新有更短的路径出现,所以要更新j到s的路径长度）for(int j = 0; j < this.m_total; j++){if (this.m_mark[j] == 0 && (this.m_matirx[k][j] + dis[k]) > 0 && (this.m_matirx[k][j] + dis[k]) < dis[j]) {                      dis[j] = this.m_matirx[k][j] + dis[k];                      this.m_matirx[s][j] = dis[j];                }  }}if (dis[e] == this.m_max){return Optional.ofNullable(null);}//this.printMatirx();return Optional.of(getShortestRoadLine(str,etr));}public static void main(String[] args){String[] points = {"1","2","3","4","5","6","7","8","9"};Map<String,Map<String,Integer>> line = new HashMap<String,Map<String,Integer>>();line.put("1", new HashMap<String,Integer>());line.get("1").put("2", 4);line.get("1").put("4", 2);line.get("1").put("3", 5);line.put("2", new HashMap<String,Integer>());line.get("2").put("1", 4);line.get("2").put("5", 3);line.put("3", new HashMap<String,Integer>());line.get("3").put("1", 5);line.get("3").put("6", 7);line.put("4", new HashMap<String,Integer>());line.get("4").put("7", 5);line.get("4").put("1", 2);line.put("5", new HashMap<String,Integer>());line.get("5").put("2", 3);line.get("5").put("7", 9);line.get("5").put("8", 4);line.put("6", new HashMap<String,Integer>());line.get("6").put("3", 7);line.get("6").put("7", 1);line.put("7", new HashMap<String,Integer>());line.get("7").put("6", 1);line.get("7").put("5", 9);line.get("7").put("4", 5);line.put("8", new HashMap<String,Integer>());line.get("8").put("5", 4);line.get("8").put("9", 3);line.put("9", new HashMap<String,Integer>());line.get("9").put("8", 3);MyDijkstra o = new MyDijkstra(points,line);Optional <LinkedList<String>> road = o.getShortestRoad("1","6");if (road.isPresent()){System.out.println("road--->" + road.get());}else{System.out.println("can not find road");}}//模拟矩阵块的最短寻路//public static void main(String[] args)//{//int width = 50;//int height = 50;//int startX = 0;//int startY = 0;//int endX = 45;//int endY = 48;//int[][] rect = new int[width][height];//for(int i = 0; i < width; i++)//{//for(int j = 0; j < height ; j++)//{//rect[i][j] = 1;//}//}////rect[startX][startY] = 2;//起点//rect[endX][endY] = 3;//终点//Random r1 = new Random(System.currentTimeMillis());//////障碍,不能通过//for(int i = 0; i < 500; i++)//{//int randX = Math.abs(r1.nextInt() % width);//int randY = Math.abs(r1.nextInt() % height);//if (rect[randX][randY] == 1)//{//rect[randX][randY] = 4;//}//}////LinkedHashMap<String,int[]> listMap = new LinkedHashMap<String,int[]>();//int pos = 0;////for(int i = 0; i < width;i++)//{//for (int j = 0; j < height;j++)//{//if (rect[i][j] != 4)//{//listMap.put(i + "_" + j, new int[]{i,j,pos++});//}//}//}////Map<String,Map<String,Integer>> line = new HashMap<String,Map<String,Integer>>();////listMap.forEach((id,node)->{//line.put(id, new HashMap<String,Integer>());//String id1 = node[0] + "_" + (node[1]  + 1);//String id2 = node[0] + "_" + (node[1]  - 1);//String id3 = (node[0] + 1) + "_" + node[1];//String id4 = (node[0] - 1) + "_" + node[1];//if (listMap.containsKey(id1))//{//line.get(id).put(id1, 1);//}//if (listMap.containsKey(id2))//{//line.get(id).put(id2, 1);//}//if (listMap.containsKey(id3))//{//line.get(id).put(id3, 1);//}//if (listMap.containsKey(id4))//{//line.get(id).put(id4, 1);//}//});////String[] node = new String[listMap.size()];////pos = 0;////for(Entry<String,int[]> entry : listMap.entrySet())//{//node[pos++] = entry.getKey();//}////MyDijkstra o = new MyDijkstra(node,line);//Optional <LinkedList<String>> road = o.getShortestRoad(startX + "_" + startY,endX + "_" + endY);//if (!road.isPresent())//{//System.out.println("can not find shortest road");//return;//}//road.get().forEach(p->{//int[] mapP = listMap.get(p);//if (rect[mapP[0]][mapP[1]] == 1)//{//rect[mapP[0]][mapP[1]] = 0;//}//});//for(int i = 0; i < width;i++)//{//for (int j = 0; j < height;j++)//{//System.out.print(rect[i][j] + " ");//}//System.out.print("\n");//}//}}