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main.cpp
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main.cpp
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// graph for mincost maxflow contains negative weight edge, can't be used in
// Calculating shortest paths.
#include <iostream>
#include <vector>
// BGL include
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/dijkstra_shortest_paths.hpp>
#include <boost/graph/push_relabel_max_flow.hpp>
using namespace std;
// Graph Type with nested interior edge properties for Cost Flow Algorithms
typedef boost::adjacency_list_traits<boost::vecS, boost::vecS, boost::directedS> traits;
typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::directedS, boost::no_property,
boost::property<boost::edge_capacity_t, long,
boost::property<boost::edge_residual_capacity_t, long,
boost::property<boost::edge_reverse_t, traits::edge_descriptor,
boost::property <boost::edge_weight_t, long> > > > > graph; // new! weightmap corresponds to costs
typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::directedS,
boost::no_property, boost::property<boost::edge_weight_t, int> > weighted_graph;
typedef traits::vertex_descriptor vertex_desc;
typedef traits::edge_descriptor edge_desc;
// Custom edge adder class
class edge_adder {
graph &G;
public:
explicit edge_adder(graph &G) : G(G) {}
void add_edge(int from, int to, long capacity, long cost) {
auto c_map = boost::get(boost::edge_capacity, G);
auto r_map = boost::get(boost::edge_reverse, G);
auto w_map = boost::get(boost::edge_weight, G); // new!
const edge_desc e = boost::add_edge(from, to, G).first;
const edge_desc rev_e = boost::add_edge(to, from, G).first;
c_map[e] = capacity;
c_map[rev_e] = 0; // reverse edge has no capacity!
r_map[e] = rev_e;
r_map[rev_e] = e;
w_map[e] = cost; // new assign cost
w_map[rev_e] = -cost; // new negative cost
}
};
vector<int> dijkstra_dist(const weighted_graph &G, int s) {
int n = boost::num_vertices(G);
std::vector<int> dist_map(n);
boost::dijkstra_shortest_paths(G, s,
boost::distance_map(boost::make_iterator_property_map(
dist_map.begin(), boost::get(boost::vertex_index, G))));
return dist_map;
}
void testcase() {
int n, m, s, f;
cin >> n >> m >> s >> f;
graph G(n);
weighted_graph G_aux(n);
edge_adder adder(G);
auto w_map = boost::get(boost::edge_weight, G); // new!
auto c_map = boost::get(boost::edge_capacity, G);
for (int i = 0; i < m; i++) {
int a, b, c, d;
cin >> a >> b >> c >> d;
if (a == b) {
continue;
}
adder.add_edge(a, b, c, d);
adder.add_edge(b, a, c, d);
boost::add_edge(a, b, d, G_aux);
boost::add_edge(b, a, d, G_aux);
}
vector<int> dist_from_s = dijkstra_dist(G_aux, s);
vector<int> dist_from_f = dijkstra_dist(G_aux, f);
int min_dist = dist_from_s[f];
auto edge_its = boost::edges(G);
auto ebeg = edge_its.first;
auto eend = edge_its.second;
for (; ebeg != eend; ebeg++) {
if (w_map[*ebeg] + dist_from_s[(*ebeg).m_source] + dist_from_f[(*ebeg).m_target] > min_dist) {
c_map[*ebeg] = 0;
}
}
cout << boost::push_relabel_max_flow(G, s, f) << endl;
}
int main() {
ios_base::sync_with_stdio(false);
int t; cin >> t;
while(t--) {
testcase();
}
}