无权最短路径算法java实现

2024年1月27日 226次阅读

无权最短路径算法java实现

  • 无权最短路径算法方法实现
  • 完整代码

代码

路径扫描

public static void unweight(Graph s) {
        Queue<Graph> q = new LinkedList<Graph>();
        s.dist = 0;
        q.add(s);
        while (q.size() != 0) {
            Graph start = q.poll();
            for (Graph sadj : start.adj) {
                if (sadj.dist == INFINITY) {
                    sadj.dist = start.dist + 1;
                    sadj.latest = start;
                    q.add(sadj);
                }
            }
        }
    }

从源点开始更新：
将源点的距离设为0，然后入队；搜索源点临近点，判断该点是否被扫描，如果没有被扫描，则将距离设为源点距离+1，并将源点设为该点上一节点。
重复该过程，直至所有点被扫描到。

通过路径扫描得到节点之间的关系以及距离。

路径打印

private static void printPath(String graphname) {
        Graph graph = find(graphname);
        if (graph.latest != null) {
            printPath(graph.latest.name);
            System.out.print("to");
        }
        System.out.println(graph.name);
    }

在通过路径扫描得到节点关系的基础上，采用递归进行路径打印，递归最里层为源点，依次往外打印指定的节点。

完整代码

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

public class DirectionShortDistance {

    public static final int INFINITY = Integer.MAX_VALUE;
    public static List<Graph> graphmap = new LinkedList<Graph>();

    static class Graph {
        public String name;
        public int dist;
        public LinkedList<Graph> adj = new LinkedList<Graph>();
        public Graph latest;
        public Graph(String name) {
            this.name = name;
        }
    }

    public static void unweight(Graph s) {

        Queue<Graph> q = new LinkedList<Graph>();

        s.dist = 0;

        while (q.size() != 0) {
            Graph start = q.poll();
            for (Graph sadj : start.adj) {
                if (sadj.dist == INFINITY) {
                    sadj.dist = start.dist + 1;
                    sadj.latest = start;
                    q.add(sadj);
                }
            }
        }
    }

    public static Graph find(String name) {
        for (Graph graph : graphmap) {
            if (graph.name.equals(name))
                return graph;
        }
        return null;
    }

    private static void printPath(String graphname) {
        Graph graph = find(graphname);
        if (graph.latest != null) {
            printPath(graph.latest.name);
            System.out.print("to");
        }
        System.out.println(graph.name);
    }

    public static void main(String[] args) throws Exception {
        Graph v1 = new Graph("v1");
        Graph v2 = new Graph("v2");
        Graph v3 = new Graph("v3");
        Graph v4 = new Graph("v4");
        Graph v5 = new Graph("v5");
        Graph v6 = new Graph("v6");
        Graph v7 = new Graph("v7");

        graphmap.add(v1);
        graphmap.add(v2);
        graphmap.add(v3);
        graphmap.add(v4);
        graphmap.add(v5);
        graphmap.add(v6);
        graphmap.add(v7);

        for (Graph g : graphmap) {
            g.dist = INFINITY;
            g.latest = null;
        }

        v1.adj.add(v2);
        v1.adj.add(v4);

        v2.adj.add(v4);
        v2.adj.add(v5);

        v3.adj.add(v1);
        v3.adj.add(v6);

        v4.adj.add(v3);
        v4.adj.add(v5);
        v4.adj.add(v6);
        v4.adj.add(v7);

        v5.adj.add(v7);

        v7.adj.add(v6);

        List<Graph> vs = new ArrayList<Graph>();
        vs.add(v1);
        vs.add(v2);
        vs.add(v3);
        vs.add(v4);
        vs.add(v5);
        vs.add(v6);
        vs.add(v7);
        unweight(v3);
        System.out.println("The shortest path from v3:");
        for (int i = 1; i <= 7; i++) {
            printPath("v" + i);
        }
    }
}
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