結果

問題 No.1301 Strange Graph Shortest Path
コンテスト
ユーザー nok0
提出日時 2020-11-07 11:49:47
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 208 ms / 3,000 ms
コード長 4,619 bytes
コンパイル時間 2,751 ms
コンパイル使用メモリ 219,748 KB
最終ジャッジ日時 2025-01-15 21:29:13
ジャッジサーバーID
（参考情報） 		judge5 / judge1
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 2
other AC * 33
権限があれば一括ダウンロードができます
コンパイルメッセージ
main.cpp: In function ‘int main()’:
main.cpp:172:14: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
  172 |         scanf("%d%d", &n, &m);
      |         ~~~~~^~~~~~~~~~~~~~~~
main.cpp:177:22: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
  177 |                 scanf("%d%d%d%d", &u, &v, &c, &d);
      |                 ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

ソースコード

diff # 

#include <bits/stdc++.h>
using namespace std;
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

namespace atcoder {

template <class Cap, class Cost>
struct mcf_graph {
public:
	mcf_graph() {}
	mcf_graph(int n) : _n(n), g(n) {}

	int add_edge(int from, int to, Cap cap, Cost cost) {
		assert(0 <= from && from < _n);
		assert(0 <= to && to < _n);
		assert(0 <= cap);
		assert(0 <= cost);
		int m = int(pos.size());
		pos.push_back({from, int(g[from].size())});
		int from_id = int(g[from].size());
		int to_id = int(g[to].size());
		if(from == to) to_id++;
		g[from].push_back(_edge{to, to_id, cap, cost});
		g[to].push_back(_edge{from, from_id, 0, -cost});
		return m;
	}

	struct edge {
		int from, to;
		Cap cap, flow;
		Cost cost;
	};

	edge get_edge(int i) {
		int m = int(pos.size());
		assert(0 <= i && i < m);
		auto _e = g[pos[i].first][pos[i].second];
		auto _re = g[_e.to][_e.rev];
		return edge{
		    pos[i].first,
		    _e.to,
		    _e.cap + _re.cap,
		    _re.cap,
		    _e.cost,
		};
	}
	std::vector<edge> edges() {
		int m = int(pos.size());
		std::vector<edge> result(m);
		for(int i = 0; i < m; i++) {
			result[i] = get_edge(i);
		}
		return result;
	}

	std::pair<Cap, Cost> flow(int s, int t) {
		return flow(s, t, std::numeric_limits<Cap>::max());
	}
	std::pair<Cap, Cost> flow(int s, int t, Cap flow_limit) {
		return slope(s, t, flow_limit).back();
	}
	std::vector<std::pair<Cap, Cost>> slope(int s, int t) {
		return slope(s, t, std::numeric_limits<Cap>::max());
	}
	std::vector<std::pair<Cap, Cost>> slope(int s, int t, Cap flow_limit) {
		assert(0 <= s && s < _n);
		assert(0 <= t && t < _n);
		assert(s != t);
		// variants (C = maxcost):
		// -(n-1)C <= dual[s] <= dual[i] <= dual[t] = 0
		// reduced cost (= e.cost + dual[e.from] - dual[e.to]) >= 0 for all edge
		std::vector<Cost> dual(_n, 0), dist(_n);
		std::vector<int> pv(_n), pe(_n);
		std::vector<bool> vis(_n);
		auto dual_ref = [&]() {
			std::fill(dist.begin(), dist.end(), std::numeric_limits<Cost>::max());
			std::fill(pv.begin(), pv.end(), -1);
			std::fill(pe.begin(), pe.end(), -1);
			std::fill(vis.begin(), vis.end(), false);
			struct Q {
				Cost key;
				int to;
				bool operator<(Q r) const { return key > r.key; }
			};
			std::priority_queue<Q> que;
			dist[s] = 0;
			que.push(Q{0, s});
			while(!que.empty()) {
				int v = que.top().to;
				que.pop();
				if(vis[v]) continue;
				vis[v] = true;
				if(v == t) break;
				// dist[v] = shortest(s, v) + dual[s] - dual[v]
				// dist[v] >= 0 (all reduced cost are positive)
				// dist[v] <= (n-1)C
				for(int i = 0; i < int(g[v].size()); i++) {
					auto e = g[v][i];
					if(vis[e.to] || !e.cap) continue;
					// |-dual[e.to] + dual[v]| <= (n-1)C
					// cost <= C - -(n-1)C + 0 = nC
					Cost cost = e.cost - dual[e.to] + dual[v];
					if(dist[e.to] - dist[v] > cost) {
						dist[e.to] = dist[v] + cost;
						pv[e.to] = v;
						pe[e.to] = i;
						que.push(Q{dist[e.to], e.to});
					}
				}
			}
			if(!vis[t]) {
				return false;
			}

			for(int v = 0; v < _n; v++) {
				if(!vis[v]) continue;
				// dual[v] = dual[v] - dist[t] + dist[v]
				//         = dual[v] - (shortest(s, t) + dual[s] - dual[t]) +
				//         (shortest(s, v) + dual[s] - dual[v]) = - shortest(s, t) +
				//         dual[t] + shortest(s, v) = shortest(s, v) - shortest(s, t) >=
				//         0 - (n-1)C
				dual[v] -= dist[t] - dist[v];
			}
			return true;
		};
		Cap flow = 0;
		Cost cost = 0, prev_cost_per_flow = -1;
		std::vector<std::pair<Cap, Cost>> result;
		result.push_back({flow, cost});
		while(flow < flow_limit) {
			if(!dual_ref()) break;
			Cap c = flow_limit - flow;
			for(int v = t; v != s; v = pv[v]) {
				c = std::min(c, g[pv[v]][pe[v]].cap);
			}
			for(int v = t; v != s; v = pv[v]) {
				auto& e = g[pv[v]][pe[v]];
				e.cap -= c;
				g[v][e.rev].cap += c;
			}
			Cost d = -dual[s];
			flow += c;
			cost += c * d;
			if(prev_cost_per_flow == d) {
				result.pop_back();
			}
			result.push_back({flow, cost});
			prev_cost_per_flow = d;
		}
		return result;
	}

private:
	int _n;

	struct _edge {
		int to, rev;
		Cap cap;
		Cost cost;
	};

	std::vector<std::pair<int, int>> pos;
	std::vector<std::vector<_edge>> g;
};

}  // namespace atcoder

int n, m, u, v, c, d;
int main() {
	scanf("%d%d", &n, &m);

	atcoder::mcf_graph<int, long long> mcf(n);

	while(m--) {
		scanf("%d%d%d%d", &u, &v, &c, &d);
		u--, v--;
		mcf.add_edge(u, v, 1, c);
		mcf.add_edge(u, v, 1, d);
		mcf.add_edge(v, u, 1, c);
		mcf.add_edge(v, u, 1, d);
	}

	auto p = mcf.flow(0, n - 1, 2);

	printf("%lld\n", p.second);

	return 0;
}
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