Error in Implementation of Dijkstra's Algorithm

Question

I am trying to attempt Dijkstra's with an Adjacency list, I can't figure out why I'm failing the test cases.

Node * n = list[source].head;
while(n)
{
    q.push(n);
    v[n->b] = n->w;
    n = n->next;
}

while(!q.empty())
{
    n = q.front();
    i = n->b;
    o = list[i].head;
    q.pop();

    while(o)
    {
        if(!v[o->b]) 
        {
            q.push(o);
            v[o->b] = v[i] + o->w;
        } 
        else if(v[o->b] > v[i] + o->w)
        {
            v[o->b] = v[i] + o->w;   
        }
        o = o->next;
    }
}

i = 0;
while(i < vertices)
{
    if(i != node)
        printf("%d ", v[i] ? v[i] : -1);
    i++;
}
cout<<"\n";

I am passing trivial test cases.

Example Input: (xyw), 1 2 3, 1 3 4, 1 4 5, 3 5 101,

Source is 1.

Output: 3 4 5 5

Example 2: 1 2 24 1 4 20 3 1 3 4 3 12

Source is 1.

Output: 24 3 15

However, I am failing the more sophisticated test cases.

Answer 1

It seems you are confusing the two arrays - one for which vertex is already visited, and one for the optimal special distances(ie optimal distance to the vertices found so far). Let's denote the visited array with v and the optimal distance array with dist .

In this statement:

if(v[o->b] > v[i] + o->w)

You need to be using dist instead of v .

After you pop a node you need to check if it is visited. If it is visited, continue on to the next node. Otherwise mark it as visited and execute the remaining logic.