139 lines
2.3 KiB
C++
139 lines
2.3 KiB
C++
#include <bits/stdc++.h> // {{{
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#include <version>
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#ifdef __cpp_lib_ranges_enumerate
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#include <ranges>
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namespace rv = std::views;
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namespace rs = std::ranges;
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#endif
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// https://codeforces.com/blog/entry/96344
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#pragma GCC optimize("O2,unroll-loops")
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#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
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using namespace std;
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using i32 = int32_t;
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using u32 = uint32_t;
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using i64 = int64_t;
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using u64 = uint64_t;
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using f64 = double;
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using f128 = long double;
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#if __cplusplus >= 202002L
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template <typename T>
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constexpr T MIN = std::numeric_limits<T>::min();
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template <typename T>
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constexpr T MAX = std::numeric_limits<T>::max();
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template <typename T>
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[[nodiscard]] static T sc(auto&& x) {
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return static_cast<T>(x);
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}
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template <typename T>
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[[nodiscard]] static T sz(auto&& x) {
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return static_cast<T>(x.size());
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}
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#endif
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static void NO() {
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std::cout << "NO\n";
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}
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static void YES() {
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std::cout << "YES\n";
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}
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template <typename T>
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using vec = std::vector<T>;
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#define all(x) (x).begin(), (x).end()
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#define rall(x) (x).rbegin(), (x).rend()
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#define ff first
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#define ss second
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#ifdef LOCAL
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#define db(...) std::print(__VA_ARGS__)
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#define dbln(...) std::println(__VA_ARGS__)
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#else
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#define db(...)
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#define dbln(...)
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#endif
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// }}}
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void solve() {
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u32 n, m;
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cin >> n >> m;
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vec<vec<u32>> tree(n + 1);
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vec<i32> par(n + 1, -1);
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par[1] = 1;
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u32 u, v;
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for (u32 i = 0; i < m; ++i) {
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cin >> u >> v;
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tree[u].push_back(v);
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tree[v].push_back(u);
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}
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queue<u32> q{{1}};
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while (!q.empty()) {
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auto node = q.front();
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q.pop();
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for (auto& neighbor : tree[node]) {
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if (par[neighbor] == -1) {
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par[neighbor] = node;
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q.push(neighbor);
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}
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}
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}
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if (par[n] == -1) {
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cout << "IMPOSSIBLE\n";
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return;
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}
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u32 cur = n;
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vec<u32> ans;
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while (cur != 1) {
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ans.push_back(cur);
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cur = par[cur];
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}
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ans.push_back(1);
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reverse(all(ans));
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cout << ans.size() << '\n';
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for (u32 i = 0; i < ans.size(); ++i) {
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cout << ans[i] << " \n"[i == ans.size() - 1];
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}
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}
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int main() { // {{{
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std::cin.exceptions(std::cin.failbit);
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#ifdef LOCAL
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std::cerr.rdbuf(std::cout.rdbuf());
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std::cout.setf(std::ios::unitbuf);
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std::cerr.setf(std::ios::unitbuf);
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#else
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std::cin.tie(nullptr)->sync_with_stdio(false);
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#endif
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u32 tc = 1;
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// std::cin >> tc;
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for (u32 t = 0; t < tc; ++t) {
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solve();
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}
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return 0;
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}
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// }}}
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