Submission #49136011

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Source Code Expand

#include <bits/stdc++.h>
#include <atcoder/modint>
#include <atcoder/dsu>

namespace {
    using ModInt [[maybe_unused]] = atcoder::modint998244353;
    using Num [[maybe_unused]] = long long int;
    using Vec [[maybe_unused]] = std::vector<Num>;
    using Set [[maybe_unused]] = std::set<Num>;
    using Mset [[maybe_unused]] = std::multiset<Num>;
    using Edges [[maybe_unused]] = std::vector<std::vector<Num>>;

    template<typename T>
    using Q [[maybe_unused]] = std::queue<T>;

    template<typename T>
    using PQ [[maybe_unused]] = std::priority_queue<T, std::vector<T>, std::greater<T>>;
}

void solve(std::istream& is, std::ostream& os) {
    Num n, m;
    is >> n >> m;

    Vec aset(n);
    for(auto&& a : aset) {
        is >> a;
    }

    std::vector<std::vector<std::pair<Num, Num>>> edges(200009);
    atcoder::dsu tree(n);

    for(Num i{0}; i<m; ++i) {
        Num u, v;
        is >> u >> v;
        --u;
        --v;

        if (aset.at(u) == aset.at(v)) {
            tree.merge(u, v);
        } else {
            if (aset.at(u) > aset.at(v)) {
                std::swap(u, v);
            }
            edges[aset[u]].push_back(std::make_pair(u, v));
        }
    }

    Vec dist(n, -1000000000000LL);
    dist.at(tree.leader(0)) = 1;

    for(const auto& vec : edges) {
        for(const auto& [from, to] : vec) {
            const auto vf = tree.leader(from);
            const auto vt = tree.leader(to);

            if (dist.at(vf) > 0) {
                dist.at(vt) = std::max(dist.at(vt), dist.at(vf) + 1);
            }
        }
    }

    const Num goal = tree.leader(n-1);
    Num ct = dist.at(goal);
    ct = (ct < 0) ? 0 : ct;
    os << ct << "\n";
}

int main(void) {
    solve(std::cin, std::cout);
    return 0;
}

Submission Info

Judge Result