用java编写的单源最短路径算法，Dijkstra算法

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package test;    import java.util.TreeMap;  import java.util.ArrayList;  import java.io.BufferedReader;  import java.io.InputStreamReader;  import java.io.IOException;    class Point {      private int id;// 点的id      private boolean flag = false;// 标志是否被遍历      int sum;// 记录总的点个数        private TreeMap<Integer, Integer> thisPointMap = new TreeMap<Integer, Integer>();// 该点到各点的距离。      BufferedReader bufr = new BufferedReader(new InputStreamReader(System.in));        Point(int sum) { // 构造函数 带有顶点个数          this.sum = sum;      }        public void setId(int id) {// 设置顶点id          this.id = id;      }        public int getId() {// 获得顶点id          return this.id;      }        public void changeFlag() {// 修改访问状态。          this.flag = true;      }        public boolean isVisit() {// 查看访问状态          return flag;      }        public void setLenToOther()throws IOException{// 初始化改点到各顶点的距离。          System.out.println("=======请输入顶点" + (this.id + 1) + "至其他各顶点的边距=======");          for (int i = 0; i < sum; i++) {              if (i == this.id)                  thisPointMap.put(this.id, 0);              else {                  System.out.print("至 顶点" + (i + 1) + " 的距离 ：");                  boolean flag =true;                  int len = 0;                  while(flag){                      try {                          len = Integer.valueOf(bufr.readLine());                          flag = false;                      } catch (NumberFormatException e) {                          System.out.print("输入有误，请重新输入：");                      }                  };                  thisPointMap.put(i, len);              }          }      }        // 该点到顶尖id的 距离。      public int lenToPointId(int id) {          return thisPointMap.get(id);      }  }    class Dijkstra {      public static void main(String[] args)throws IOException {          ArrayList<Point> point_arr = new ArrayList<Point>();// 存储点集合          BufferedReader bufr = new BufferedReader(new InputStreamReader(System.in));          System.out.print("请输入顶点个数： ");          int sum = 0;          boolean flag =true;          while(flag){              try {                  sum = Integer.valueOf(bufr.readLine());                  flag = false;              } catch (NumberFormatException e) {                  System.out.print("输入有误，请重新输入：");              }          };          for (int i = 0; i < sum; i++) {// 初始化              Point p = new Point(sum);              p.setId(i);              p.setLenToOther();              point_arr.add(p);          }          System.out.print("请输入起始顶点 id ：");          boolean flag2 =true;          int start = 0;          while(flag2){              try {                  start = Integer.valueOf(bufr.readLine())-1;                  if(start > sum-1 || start < 0)                      throw new NumberFormatException();                  flag2 = false;              }catch (NumberFormatException e) {                  System.out.print("输入有误，请重新输入：");              }          };          showDijkstra(point_arr, start);// 单源最短路径遍历      }        public static void showDijkstra(ArrayList<Point> arr, int i) {          System.out.print("顶点" + (i + 1));          arr.get(i).changeFlag();          Point p1 = getTopointMin(arr, arr.get(i));          if (p1 == null)              return;          int id = p1.getId();          showDijkstra(arr, id);        }        public static Point getTopointMin(ArrayList<Point> arr, Point p) {          Point temp = null;          int minLen = Integer.MAX_VALUE;          for (int i = 0; i < arr.size(); i++) {              // 当已访问 或 者是自身或者无该路径时跳过。              if (arr.get(i).isVisit() || arr.get(i).getId() == p.getId() || p.lenToPointId(i) < 0)                  continue;              else {                  if (p.lenToPointId(i) < minLen) {                      minLen = p.lenToPointId(i);                      temp = arr.get(i);                  }              }          }          if (temp == null)              return temp;          else              System.out.print("  @--" + minLen + "--> ");          return temp;      }  }
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