Pagini recente » Cod sursa (job #2573192) | Cod sursa (job #3261858) | Cod sursa (job #2981435) | Cod sursa (job #76849) | Cod sursa (job #2954330)
#include <iostream>
#include <fstream>
#include <queue>
#include <unordered_map>
#include <vector>
#include <limits>
using namespace std;
class Graph {
private:
int _nodes, _edges;
vector<unordered_map<int, int>> _residual_graph;
vector<int> _bfs_tree;
vector<bool> _visited;
vector<unordered_map<int, int>> _adj_list;
bool BFS(const int start, const int dest) {
queue<int> node_queue;
_visited = vector<bool>(_nodes + 1);
_bfs_tree = vector<int>(_nodes + 1);
_bfs_tree[start] = 0;
_visited[start] = true;
node_queue.push(start);
while (!node_queue.empty()) {
const int node = node_queue.front();
node_queue.pop();
for (auto& edge : _residual_graph[node]) {
if (!_visited[edge.first] && edge.second > 0) {
_visited[edge.first] = true;
_bfs_tree[edge.first] = node;
node_queue.push(edge.first);
}
}
}
return _visited[dest];
}
public:
Graph(int nodes, int edges, vector<unordered_map<int, int>> adj_list) :
_nodes(nodes),
_edges(edges),
_residual_graph(adj_list),
_adj_list(std::move(adj_list))
{
for (int i = 1; i <= _nodes; ++i) {
for (const auto& edge : _adj_list[i]) {
if(_residual_graph[edge.first].find(i) == _residual_graph[edge.first].end())
_residual_graph[edge.first][i] = 0;
}
}
}
int maxFlow(const int source,const int dest){
int max_flux = 0;
while(BFS(source,dest)){
for (const auto& edge : _residual_graph[dest]) {
int node = edge.first;
if (edge.second == _adj_list[node][dest] || !_visited[node])
continue;
int flux = numeric_limits<int>::max();
flux = min(flux, _residual_graph[node][dest]);
while (_bfs_tree[node] != 0) {
const int father = _bfs_tree[node];
flux = min(flux, _residual_graph[father][node]);
if (flux == 0)
break;
node = father;
}
if (flux == 0)
continue;
max_flux += flux;
node = edge.first;
_residual_graph[node][dest] -= flux;
_residual_graph[dest][node] += flux;
while (_bfs_tree[node] != 0) {
const int father = _bfs_tree[node];
_residual_graph[father][node] -= flux;
_residual_graph[node][father] += flux;
node = father;
}
}
}
return max_flux;
}
};
int main()
{
ifstream in("maxflow.in");
int nodes, edges;
in >> nodes >> edges;
vector<unordered_map<int, int>> adj_list(nodes + 1);
for(int i=0; i<edges; ++i){
int node1, node2, capacity;
in >> node1 >> node2 >> capacity;
adj_list[node1][node2] = capacity;
}
in.close();
Graph flux_time(nodes, edges, adj_list);
ofstream out("maxflow.out");
out << flux_time.maxFlow(1,nodes);
out.close();
}