Abdelrahman Said
153 lines
3.6 KiB
C
153 lines
3.6 KiB
C
// vim:fileencoding=utf-8:foldmethod=marker
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/* graph.c
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A generic adjacency list graph data type.
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*/
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/* Copyright 2003-2020 by Steven S. Skiena; all rights reserved.
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Permission is granted for use in non-commerical applications
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provided this copyright notice remains intact and unchanged.
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These programs appear in my books:
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"The Algorithm Design Manual" by Steven Skiena, second edition, Springer,
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London 2008. See out website www.algorist.com for additional information
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or https://www.amazon.com/exec/obidos/ASIN/1848000693/thealgorith01-20
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"Programming Challenges: The Programming Contest Training Manual"
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by Steven Skiena and Miguel Revilla, Springer-Verlag, New York 2003.
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See our website www.programming-challenges.com for additional information,
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or https://www.amazon.com/exec/obidos/ASIN/0387001638/thealgorithmrepo/
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include "queue.h"
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#include "graph.h"
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/* [[[ init_graph_c */
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void initialize_graph(graph *g, bool directed) {
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int i; /* counter */
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g->nvertices = 0;
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g->nedges = 0;
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g->directed = directed;
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for (i = 1; i <= MAXV; i++) {
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g->degree[i] = 0;
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}
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for (i = 1; i <= MAXV; i++) {
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g->edges[i] = NULL;
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}
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}
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/* ]]] */
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/* [[[ insert_edge_cut */
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void insert_edge(graph *g, int x, int y, bool directed) {
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edgenode *p; /* temporary pointer */
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p = malloc(sizeof(edgenode)); /* allocate edgenode storage */
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p->weight = 0;
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p->y = y;
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p->next = g->edges[x];
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g->edges[x] = p; /* insert at head of list */
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g->degree[x]++;
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if (!directed) {
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insert_edge(g, y, x, true);
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} else {
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g->nedges++;
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}
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}
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/* ]]] */
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/* [[[ read_graph_cut */
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void read_graph(graph *g, bool directed) {
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int i; /* counter */
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int m; /* number of edges */
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int x, y; /* vertices in edge (x,y) */
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initialize_graph(g, directed);
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scanf("%d %d", &(g->nvertices), &m);
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for (i = 1; i <= m; i++) {
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scanf("%d %d", &x, &y);
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insert_edge(g, x, y, directed);
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}
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}
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/* ]]] */
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void delete_edge(graph *g, int x, int y, bool directed) {
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edgenode *p, *p_back; /* temporary pointers */
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p = g->edges[x];
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p_back = NULL;
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while (p != NULL) {
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if (p->y == y) {
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g->degree[x]--;
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if (p_back != NULL) {
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p_back->next = p->next;
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} else {
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g->edges[x] = p->next;
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}
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free(p);
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if (!directed) {
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delete_edge(g, y, x, true);
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} else {
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g->nedges--;
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}
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return;
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} else {
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p = p->next;
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}
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}
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printf("Warning: deletion(%d,%d) not found in g.\n",x,y);
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}
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/* [[[ print_graph_cut */
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void print_graph(graph *g) {
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int i; /* counter */
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edgenode *p; /* temporary pointer */
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for (i = 1; i <= g->nvertices; i++) {
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printf("%d: ", i);
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p = g->edges[i];
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while (p != NULL) {
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printf(" %d", p->y);
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p = p->next;
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}
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printf("\n");
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}
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}
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/* ]]] */
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/* [[[ graph_transpose_cut */
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graph *transpose(graph *g) {
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graph *gt; /* transpose of graph g */
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int x; /* counter */
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edgenode *p; /* temporary pointer */
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gt = (graph *) malloc(sizeof(graph));
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initialize_graph(gt, true); /* initialize directed graph */
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gt->nvertices = g->nvertices;
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for (x = 1; x <= g->nvertices; x++) {
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p = g->edges[x];
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while (p != NULL) {
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insert_edge(gt, p->y, x, true);
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p = p->next;
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}
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}
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return(gt);
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}
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/* ]]] */
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