Shortest tour

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <climits>
#include <set>
#include <queue>

using namespace std;

struct Vertex {
    int index;
    int number = -1;
    vector<int> neighbours;
    bool isFinish = false;

    Vertex(int index) : index(index) {}

    void add(int neighbour) {
        neighbours.push_back(neighbour);
    }
};

vector<Vertex*> vertexes;

int getLen(int start) {
    priority_queue<pair<int, pair<int, int>>, vector<pair<int, pair<int, int>>>, greater<pair<int, pair<int, int>>>> next;
    //currLen, index, addedInSearchFor
    next.push({ 0, {start, 0} });
    set<int> inCurrSearch;
    int currSearch = 0;
    while (!next.empty()) {
        int currLen = next.top().first;
        int currIndex = next.top().second.first;
        next.pop();
        if (inCurrSearch.find(currIndex) != inCurrSearch.end())
            continue;
        inCurrSearch.insert(currIndex);
        if (vertexes[currIndex]->number == currSearch) {
            currSearch++;
            inCurrSearch.clear();
            if (vertexes[currIndex]->isFinish) {
                return currLen;
            }
        }

        for (int neighbour : vertexes[currIndex]->neighbours) {
            if (vertexes[neighbour]->number <= currSearch)
                next.push({ currLen + 1, {neighbour, currSearch} });
        }
        while (!next.empty() && next.top().second.second < currSearch)
            next.pop();
    }
    return -1;
}

int main() {
    int n, m, a, b, k, start;
    cin >> n >> m;

    for (int i = 0; i < n; i++) {
        vertexes.push_back(new Vertex(i));
    }

    for (int i = 0; i < m; i++) {
        cin >> a >> b;
        if (a == b)
        {
            continue;
        }
        vertexes[a]->add(b);
    }

    cin >> k;

    for (int i = 0; i < k; i++) {
        cin >> a;
        vertexes[a]->number = i;
        if (i == 0)
            start = a;
    }
    vertexes[a]->isFinish = true;
    cout << getLen(start);
    return 0;
}