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1731. [USACO 2005 Dec] Layout 排队布局
https://hydro.ac/d/bzoj/record/63b6d364291ec3514f4e3b50
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BZOJ/1731/1731.cpp
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82
BZOJ/1731/1731.cpp
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#include <iostream>
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#include <algorithm>
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#include <iterator>
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#include <queue>
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#include <vector>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 1005;
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const int INF = 0x3f3f3f3f;
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int n, ml, md, cnt[N], dist[N];
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std::vector<std::pair<int, int>> g[N];
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bool vis[N];
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bool spfa() {
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std::fill(std::begin(cnt), std::end(cnt), 0);
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std::fill(std::begin(vis), std::end(vis), false);
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std::fill(std::begin(dist), std::end(dist), INF);
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std::queue<int> q;
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q.emplace(1);
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dist[1] = 0;
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vis[1] = true;
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while (!q.empty()) {
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int u = q.front();
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q.pop();
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vis[u] = false;
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for (auto e : g[u]) {
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int v = e.first,
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w = e.second;
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if (dist[v] > dist[u] + w) {
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dist[v] = dist[u] + w;
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if (!vis[v]) {
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cnt[v] = cnt[u] + 1;
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if (cnt[v] >= n) return false;
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vis[v] = true;
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q.emplace(v);
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}
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}
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}
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}
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return true;
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}
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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cin >> n >> ml >> md;
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for (int i = 1, a, b, c; i <= ml; i++) {
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cin >> a >> b >> c;
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g[a].emplace_back(b, c);
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}
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for (int i = 1, a, b, c; i <= md; i++) {
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cin >> a >> b >> c;
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g[b].emplace_back(a, -c);
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}
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if (!spfa()) {
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cout << -1 << endl;
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} else {
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cout << (dist[n] == INF ? -2 : dist[n]) << endl;
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}
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return 0;
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}
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