% This file is part of the Stanford GraphBase (c) Stanford University 1992 \def\title{QUEEN} @i boilerplate.w %<< legal stuff: PLEASE READ IT BEFORE MAKING ANY CHANGES! @* Introduction. This is a short demonstration of how to generate and traverse graphs with the Stanford GraphBase. It creates a graph with 12 vertices, representing the positions on a $3\times4$ rectangular board; two positions are considered adjacent if you can get from one to another by a queen move. Then it prints a description of the vertices and their neighbors, on the standard output file. An ASCII file called \.{queen.gb} is also produced. Other programs can make a copy of the queen graph by calling |restore_graph("queen.gb")|. You may find it interesting to compare the output of |queen| with the contents of \.{queen.gb}; the former is intended to be readable by human beings, the latter by computers. @f Graph int /* |gb_graph| defines the |Graph| type and a few others */ @f Vertex int @f Arc int @p #include "gb_graph.h" /* we use the |gb_graph| data structures */ #include "gb_basic.h" /* we test the basic graph operations */ #include "gb_save.h" /* and we save our results in ASCII format */ @# main() {@+Graph *g,*gg,*ggg; g=board(3,4,0,0,-1,0,0); /* a graph with rook moves */ gg=board(3,4,0,0,-2,0,0); /* a graph with bishop moves */ ggg=gunion(g,gg,0,0); /* a graph with queen moves */ save_graph(ggg,"queen.gb"); /* generate an ASCII file for |ggg| */ @; } @ @= if (ggg==NULL) printf("Something went wrong (panic code %d)!\n",panic_code); else { register Vertex *v; /* current vertex being visited */ printf("Queen Moves on a 3x4 Board\n\n"); printf(" The graph whose official name is\n%s\n", ggg->id); printf(" has %d vertices and %d arcs:\n\n", ggg->n, ggg->m); for (v=ggg->vertices; vvertices+ggg->n; v++) { register Arc *a; /* current arc from |v| */ printf("%s\n", v->name); for (a=v->arcs; a; a=a->next) printf(" -> %s, length %d\n", a->tip->name, a->len); } } @* Index.