boost/graph/read_dimacs.hpp
//======================================================================= // Copyright 1997, 1998, 1999, 2000 University of Notre Dame. // Authors: Jeremy G. Siek, Andrew Lumsdaine, Lie-Quan Lee // // Distributed under the Boost Software License, Version 1.0. (See // accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) //======================================================================= /* Reads maximal flow problem in extended DIMACS format. This works, but could use some polishing. */ /* ----------------------------------------------------------------- */ #ifndef BOOST_GRAPH_READ_DIMACS_HPP #define BOOST_GRAPH_READ_DIMACS_HPP #include <vector> #include <iostream> #include <string> #include <cstdio> #include <cstring> #include <cstdlib> #include <boost/graph/graph_traits.hpp> namespace boost { namespace detail { template < class Graph, class CapacityMap, class ReverseEdgeMap > int read_dimacs_max_flow_internal(Graph& g, CapacityMap capacity, ReverseEdgeMap reverse_edge, typename graph_traits< Graph >::vertex_descriptor& src, typename graph_traits< Graph >::vertex_descriptor& sink, std::istream& in, bool require_source_and_sink, const std::string& problem_type) { // const int MAXLINE = 100; /* max line length in the input file // */ const int ARC_FIELDS = 3; /* no of fields in arc line */ const int NODE_FIELDS = 2; /* no of fields in node line */ const int P_FIELDS = 3; /* no of fields in problem line */ typedef typename graph_traits< Graph >::vertex_descriptor vertex_descriptor; typedef typename graph_traits< Graph >::edge_descriptor edge_descriptor; std::vector< vertex_descriptor > verts; long m, n, /* number of edges and nodes */ i, head, tail, cap; long no_lines = 0, /* no of current input line */ no_plines = 0, /* no of problem-lines */ no_nslines = 0, /* no of node-source-lines */ no_nklines = 0, /* no of node-source-lines */ no_alines = 0; /* no of arc-lines */ std::string in_line; /* for reading input line */ char pr_type[4]; /* for reading type of the problem */ char nd; /* source (s) or sink (t) */ int k, /* temporary */ err_no; /* no of detected error */ /* -------------- error numbers & error messages ---------------- */ const int EN1 = 0; const int EN2 = 1; const int EN3 = 2; const int EN4 = 3; // const int EN6 = 4; // const int EN10 = 5; // const int EN7 = 6; const int EN8 = 7; const int EN9 = 8; const int EN11 = 9; const int EN12 = 10; // const int EN13 = 11; const int EN14 = 12; const int EN16 = 13; const int EN15 = 14; const int EN17 = 15; const int EN18 = 16; const int EN21 = 17; const int EN19 = 18; const int EN20 = 19; const int EN22 = 20; static const char* err_message[] = { /* 0*/ "more than one problem line.", /* 1*/ "wrong number of parameters in the problem line.", /* 2*/ "it is not a Max Flow problem line.", /* 3*/ "bad value of a parameter in the problem line.", /* 4*/ "can't obtain enough memory to solve this problem.", /* 5*/ "more than one line with the problem name.", /* 6*/ "can't read problem name.", /* 7*/ "problem description must be before node description.", /* 8*/ "this parser doesn't support multiply sources and sinks.", /* 9*/ "wrong number of parameters in the node line.", /*10*/ "wrong value of parameters in the node line.", /*11*/ " ", /*12*/ "source and sink descriptions must be before arc descriptions.", /*13*/ "too many arcs in the input.", /*14*/ "wrong number of parameters in the arc line.", /*15*/ "wrong value of parameters in the arc line.", /*16*/ "unknown line type in the input.", /*17*/ "reading error.", /*18*/ "not enough arcs in the input.", /*19*/ "source or sink doesn't have incident arcs.", /*20*/ "can't read anything from the input file." }; /* --------------------------------------------------------------- */ /* The main loop: - reads the line of the input, - analyses its type, - checks correctness of parameters, - puts data to the arrays, - does service functions */ while (std::getline(in, in_line)) { ++no_lines; switch (in_line[0]) { case 'c': /* skip lines with comments */ case '\n': /* skip empty lines */ case '\0': /* skip empty lines at the end of file */ break; case 'p': /* problem description */ if (no_plines > 0) /* more than one problem line */ { err_no = EN1; goto error; } no_plines = 1; if ( /* reading problem line: type of problem, no of nodes, no of arcs */ std::sscanf( in_line.c_str(), "%*c %3s %ld %ld", pr_type, &n, &m) != P_FIELDS) /*wrong number of parameters in the problem line*/ { err_no = EN2; goto error; } if (pr_type != problem_type) /*wrong problem type*/ { err_no = EN3; goto error; } if (n <= 0 || m <= 0) /*wrong value of no of arcs or nodes*/ { err_no = EN4; goto error; } { for (long vi = 0; vi < n; ++vi) verts.push_back(add_vertex(g)); } break; case 'n': /* source(s) description */ if (no_plines == 0) /* there was not problem line above */ { err_no = EN8; goto error; } /* reading source or sink */ k = std::sscanf(in_line.c_str(), "%*c %ld %c", &i, &nd); --i; // index from 0 if (k < NODE_FIELDS) /* node line is incorrect */ { err_no = EN11; goto error; } if (i < 0 || i > n) /* wrong value of node */ { err_no = EN12; goto error; } switch (nd) { case 's': /* source line */ if (no_nslines != 0) /* more than one source line */ { err_no = EN9; goto error; } no_nslines = 1; src = verts[i]; break; case 't': /* sink line */ if (no_nklines != 0) /* more than one sink line */ { err_no = EN9; goto error; } no_nklines = 1; sink = verts[i]; break; default: /* wrong type of node-line */ err_no = EN12; goto error; } break; case 'a': /* arc description */ if (require_source_and_sink && (no_nslines == 0 || no_nklines == 0)) /* there was not source and sink description above */ { err_no = EN14; goto error; } if (no_alines >= m) /*too many arcs on input*/ { err_no = EN16; goto error; } if ( /* reading an arc description */ std::sscanf( in_line.c_str(), "%*c %ld %ld %ld", &tail, &head, &cap) != ARC_FIELDS) /* arc description is not correct */ { err_no = EN15; goto error; } --tail; // index from 0, not 1 --head; if (tail < 0 || tail > n || head < 0 || head > n) /* wrong value of nodes */ { err_no = EN17; goto error; } { edge_descriptor e1, e2; bool in1, in2; boost::tie(e1, in1) = add_edge(verts[tail], verts[head], g); boost::tie(e2, in2) = add_edge(verts[head], verts[tail], g); if (!in1 || !in2) { std::cerr << "unable to add edge (" << head << "," << tail << ")" << std::endl; return -1; } capacity[e1] = cap; capacity[e2] = 0; reverse_edge[e1] = e2; reverse_edge[e2] = e1; } ++no_alines; break; default: /* unknown type of line */ err_no = EN18; goto error; } /* end of switch */ } /* end of input loop */ /* ----- all is red or error while reading ----- */ if (in.eof() == 0) /* reading error */ { err_no = EN21; goto error; } if (no_lines == 0) /* empty input */ { err_no = EN22; goto error; } if (no_alines < m) /* not enough arcs */ { err_no = EN19; goto error; } if (require_source_and_sink && (out_degree(src, g) == 0 || out_degree(sink, g) == 0)) /* no arc goes out of the source */ { err_no = EN20; goto error; } /* Thanks God! all is done */ return (0); /* ---------------------------------- */ error: /* error found reading input */ std::printf( "\nline %ld of input - %s\n", no_lines, err_message[err_no]); return -1; } /* -------------------- end of parser -------------------*/ } // namespace detail template < class Graph, class CapacityMap, class ReverseEdgeMap > int read_dimacs_max_flow(Graph& g, CapacityMap capacity, ReverseEdgeMap reverse_edge, typename graph_traits< Graph >::vertex_descriptor& src, typename graph_traits< Graph >::vertex_descriptor& sink, std::istream& in = std::cin) { return detail::read_dimacs_max_flow_internal( g, capacity, reverse_edge, src, sink, in, true, "max"); } template < class Graph, class CapacityMap, class ReverseEdgeMap > int read_dimacs_min_cut(Graph& g, CapacityMap capacity, ReverseEdgeMap reverse_edge, std::istream& in = std::cin) { typename graph_traits< Graph >::vertex_descriptor dummy_src, dummy_sink; // Not filled in return detail::read_dimacs_max_flow_internal( g, capacity, reverse_edge, dummy_src, dummy_sink, in, false, "cut"); } } // namespace boost #endif // BOOST_GRAPH_READ_DIMACS_HPP