5.21

周二

/**
 * 计算最短路径长度
 */
public static int calculateShortestPath(int[][] adjacencyMatrix, String start, String end, Map<String, Integer> stationIdMap) {
    int numStations = adjacencyMatrix.length;
    boolean[] visited = new boolean[numStations];
    int[] shortestDistances = new int[numStations];

    // 初始化距离数组
    for (int i = 0; i < numStations; i++) {
        shortestDistances[i] = Integer.MAX_VALUE;
    }

    // 获取起始站和终点站的ID
    int startId = stationIdMap.get(start);
    int endId = stationIdMap.get(end);

    shortestDistances[startId] = 0;

    // 计算最短路径
    for (int i = 0; i < numStations - 1; i++) {
        int minDistance = Integer.MAX_VALUE;
        int nearestStation = -1;

        // 选择未访问的最近站点
        for (int station = 0; station < numStations; station++) {
            if (!visited[station] && shortestDistances[station] < minDistance) {
                nearestStation = station;
                minDistance = shortestDistances[station];
            }
        }

        // 标记选择的站点为已访问
        visited[nearestStation] = true;

        // 更新与选择站点相邻的站点的距离
        for (int nextStation = 0; nextStation < numStations; nextStation++) {
            if (!visited[nextStation] && adjacencyMatrix[nearestStation][nextStation] != 0 &&
                    shortestDistances[nearestStation] != Integer.MAX_VALUE &&
                    shortestDistances[nearestStation] + adjacencyMatrix[nearestStation][nextStation] < shortestDistances[nextStation]) {
                shortestDistances[nextStation] = shortestDistances[nearestStation] + adjacencyMatrix[nearestStation][nextStation];
            }
        }
    }

    return shortestDistances[endId];
}