RUPCday3Dより. tupleやpairをこんな感じで使ってますという例

dijkstra_tuple.cpp

    using Vertex = tuple<int, int, int>; // {i, j, k}
    using State = pair<int, Vertex>;
    priority_queue<State, vector<State>, greater<State>> pq; // cost, vertex
    vvvi d(n, vvi(c + 1, vi(2, inf)));
    d[0][v0][0] = 0;
    pq.push(State(0, make_tuple(0, v0, 0)));
 
    while (!pq.empty()) {
        int cost;
        Vertex vertex;
        tie(cost, vertex) = pq.top(); pq.pop();
        int i, j, k;
        tie(i, j, k) = vertex;
        if (d[i][j][k] < cost) continue;
        for (const auto& e : G[i]) {
            int ni = e.to;
            int nj = (a * j + b) % c;
            int nk = k ? 1 : (i == n - 1);
            int edge_cost = e.cost * j;
            if (d[ni][nj][nk] > cost + edge_cost) {
                d[ni][nj][nk] = cost + edge_cost;
                pq.push(State(d[ni][nj][nk], Vertex(ni, nj, nk)));
            }
        }
    }