dijkstra算法求最短路径java代码

以下是 Dijkstra 算法求最短路径的 Java 代码实现：

import java.util.*;

public class DijkstraAlgorithm {

    private static final int NO_PARENT = -1;

    private static void dijkstra(int[][] adjacencyMatrix, int startVertex) {
        int nVertices = adjacencyMatrix[0].length;

        int[] shortestDistances = new int[nVertices];
        boolean[] visited = new boolean[nVertices];

        for (int i = 0; i < nVertices; i++) {
            shortestDistances[i] = Integer.MAX_VALUE;
            visited[i] = false;
        }

        shortestDistances[startVertex] = 0;

        int[] parents = new int[nVertices];
        parents[startVertex] = NO_PARENT;

        for (int i = 1; i < nVertices; i++) {
            int nearestVertex = -1;
            int shortestDistance = Integer.MAX_VALUE;
            for (int j = 0; j < nVertices; j++) {
                if (!visited[j] && shortestDistances[j] < shortestDistance) {
                    nearestVertex = j;
                    shortestDistance = shortestDistances[j];
                }
            }

            visited[nearestVertex] = true;

            for (int k = 0; k < nVertices; k++) {
                int edgeDistance = adjacencyMatrix[nearestVertex][k];

                if (edgeDistance > 0 && ((shortestDistance + edgeDistance) < shortestDistances[k])) {
                    parents[k] = nearestVertex;
                    shortestDistances[k] = shortestDistance + edgeDistance;
                }
            }
        }

        printSolution(startVertex, shortestDistances, parents);
    }

    private static void printSolution(int startVertex, int[] distances, int[] parents) {
        int nVertices = distances.length;
        System.out.print("Vertex\t Distance\tPath");

        for (int i = 0; i < nVertices; i++) {
            if (i != startVertex) {
                System.out.print("\n" + startVertex + " -> ");
                System.out.print(i + " \t\t ");
                System.out.print(distances[i] + "\t\t");
                printPath(i, parents);
            }
        }
    }

    private static void printPath(int currentVertex, int[] parents) {
        if (currentVertex == NO_PARENT) {
            return;
        }
        printPath(parents[currentVertex], parents);
        System.out.print(currentVertex + " ");
    }

    public static void main(String[] args) {
        int[][] adjacencyMatrix = {
                {0, 4, 0, 0, 0, 0, 0, 8, 0},
                {4, 0, 8, 0, 0, 0, 0, 11, 0},
                {0, 8, 0, 7, 0, 4, 0, 0, 2},
                {0, 0, 7, 0, 9, 14, 0, 0, 0},
                {0, 0, 0, 9, 0, 10, 0, 0, 0},
                {0, 0, 4, 14, 10, 0, 2, 0, 0},
                {0, 0, 0, 0, 0, 2, 0, 1, 6},
                {8, 11, 0, 0, 0, 0, 1, 0, 7},
                {0, 0, 2, 0, 0, 0, 6, 7, 0}
        };

        dijkstra(adjacencyMatrix, 0);
    }
}

上述代码演示了一个 9 个节点的图，其中每个节点都代表一个城市，而边缘的权重代表这些城市之间的距离。在 `main` 方法中，我们定义了这个图的邻接矩阵，并选择了从第一个节点（即城市 A）开始运行 Dijkstra 算法。最后，我们调用 `dijkstra` 方法来打印最短路径和距离。