Traversing a vector of list

/* struct represents edges for a directed graph */
struct Edge {
public:
    Edge(int aTo = 0, int aCost = 0) {
        to = aTo;
        cost = aCost;
    }
    int to;
    int cost;
};

/* Graph object is used store graph using adjacency list 
method and implements Dijkstra's Algorithm to produce 
the shortest path from vertex s to all other vertices */

class Graph {
public:
    vector<int> Dijkstra(int src) const {
        // My method (stated below) goes here
    }

private:
    ...
    vector<list<Edge> > adjacencyList;
}

My question then is how do I traverse a list of edges in order to insert into a heap?

For example ( Note: (#) represents index of vector array), let's say we have 3 vertices and adjacency List representation is the following:

(0) 0 --> 1 --> 2 --> null
(1) 1 --> 2 --> null
(2) 2 --> null

I want the first vertex, vertex 0, and want to access the vertices 1 & 2 to retrieve the cost to get to each to put on another data structure (i.e. heap).

My approach was the following:

for (auto it = adjacencyList.at(0).begin(); it != 
     adjancencyList.at(0).end(); it++) {
    // use it pointer to access each vertex's cost
}

this produces error:

Value of type 'std::__1::__list_const_iterator<Edge, void *>' 
is not contextually convertible to 'bool'

Let me know if more clarification needed.