java - 为什么Dijkstra的算法对给定的图形不起作用？

我有下面的代码，dijkstra的算法，我用Wikipedia's article on the algorithm编写的。
对于给定的图（见图）和起始节点（1），它返回5作为到节点（4）的距离，这显然是错误的。但是，当从节点（4）开始时，它返回4作为到（1）的距离，这是正确的。我的密码怎么了？

//source = starting point, adj[] = adjacency list
private static int dijkstra (int source, ArrayList<Road>[] adj) {
    HashSet<Integer> vertices = new HashSet<>();

    int[] dist = new int[adj.length];
    int[] prev = new int[adj.length];

    for (int i = 0; i < adj.length; i++) {
        dist[i] = Integer.MAX_VALUE;
        prev[i] = Integer.MAX_VALUE;
        vertices.add(i);
    }

    dist[source] = 0;

    while (!vertices.isEmpty()) {
        int current = Integer.MAX_VALUE;
        for (int v: vertices) {
            if (dist[v] < current) {
                current = v;
            }
        }
        vertices.remove(current);

        for (Road v: adj[current]) {
            int alt = dist[current] + v.distance;

            if (alt < dist[v.end]) {
                dist[v.end] = alt;
                prev[v.end] = current;
            }
        }
    }
}

class Road {
    int end;
    int distance;
}

//This loop builds adjacency list from input such as "1 3 2", where 1 represents
// starting node, 3 represents end node and 2 represents weight of that edge.
//start and end values are decremented in order to be 0-indexed

for (int i = 0; i < M; i++) {
    int start = in.nextInt() - 1;
    int end = in.nextInt() - 1 ;
    int dist = in.nextInt();

    adj[start].add(new Road(end, dist));
    adj[end].add(new Road(start, dist));
}

最佳答案

这段代码导致错误：

int current = Integer.MAX_VALUE;
for (int v: vertices) {
    if (dist[v] < current) {
        current = v;
    }
}

我假设它应该搜索从起始顶点起具有最短路径的未访问节点但这应该是这样的：

int currentPathLen = Integer.MAX_VALUE, current = -1;
for (int v: vertices) {
    if (dist[v] < currentPathLen) {
        current = v;
        currentPathLen = dist[current];
    }
}