diff --git a/Luogu/P6822/P6822.cpp b/Luogu/P6822/P6822.cpp new file mode 100644 index 00000000..280c634f --- /dev/null +++ b/Luogu/P6822/P6822.cpp @@ -0,0 +1,108 @@ +#include +#include +#include +#include +#include +#include +#include + +using std::cin; +using std::cout; +const char endl = '\n'; + +const int N = 1e5 + 5, + M = 2e5 + 5; +const long long INF = 0x3f3f3f3f'3f3f3f3f; + +int n, m, s, t; +std::vector> g[N]; +std::vector> g2[M << 1]; +long long dist[M << 1]; +bool vis[M << 1]; + +void dijkstra() { + std::fill(std::begin(dist), std::end(dist), INF); + std::fill(std::begin(vis), std::end(vis), false); + + std::priority_queue, std::vector>, std::greater<>> q; + + q.emplace(0, s); + dist[s] = 0; + + while (!q.empty()) { + long long l; + int u; + + std::tie(l, u) = q.top(); + + q.pop(); + + if (vis[u]) continue; + + for (auto e : g2[u]) { + int v = e.first, + w = e.second; + + if (dist[v] > l + w) { + dist[v] = l + w; + + q.emplace(dist[v], v); + } + } + + vis[u] = true; + } +} + +int main() { + std::ios::sync_with_stdio(false); + cin.tie(nullptr); + + cin >> n >> m; + + for (int i = 1, u, v, w; i <= m; i++) { + cin >> u >> v >> w; + + g[u].emplace_back(v, w, i << 1); + g[v].emplace_back(u, w, i << 1 | 1); + } + + s = 0, t = 2 * m + 2; + + for (int i = 1; i <= n; i++) { + std::sort(g[i].begin(), g[i].end(), [](const std::tuple &lhs, const std::tuple &rhs) { + return std::get<1>(lhs) < std::get<1>(rhs); + }); + + for (int j = 0; j < g[i].size(); j++) { + int v, w, id; + + std::tie(v, w, id) = g[i][j]; + + g2[id ^ 1].emplace_back(id, w); + + if (i == 1) { + g2[s].emplace_back(id, w); + } + + if (v == n) { + g2[id].emplace_back(t, w); + } + + if (j != 0) { + int w2, id2; + + std::tie(std::ignore, w2, id2) = g[i][j - 1]; + + g2[id2].emplace_back(id, w - w2); + g2[id].emplace_back(id2, 0); + } + } + } + + dijkstra(); + + cout << dist[t] << endl; + + return 0; +}