隣接行列のデータをファイルから読み込む

グラフのデータが書き込まれているファイルからデータを読み込むプログラムがあるのですが,以下のようなコードの場合グラフのデータファイルをどのように書けばいいのかわかりません.

struct Graph {
	int nodes;
	int edges;
	int* nindex;
	int* nlist;
	int* eweight;
};

Graph readGraph(const char* const fname)
{
	Graph g;
	int cnt;

	FILE* f = fopen(fname, "rb");  if (f == NULL) { fprintf(stderr, "ERROR: could not open file %s\n\n", fname);  exit(-1); }
	cnt = fread(&g.nodes, sizeof(g.nodes), 1, f);  if (cnt != 1) { fprintf(stderr, "ERROR: failed to read nodes\n\n");  exit(-1); }
	cnt = fread(&g.edges, sizeof(g.edges), 1, f);  if (cnt != 1) { fprintf(stderr, "ERROR: failed to read edges\n\n");  exit(-1); }
	if ((g.nodes < 1) || (g.edges < 0)) { fprintf(stderr, "ERROR: node or edge count too low\n\n");  exit(-1); }

	g.nindex = (int*)malloc((g.nodes + 1) * sizeof(g.nindex[0]));
	g.nlist = (int*)malloc(g.edges * sizeof(g.nlist[0]));
	g.eweight = (int*)malloc(g.edges * sizeof(g.eweight[0]));
	if ((g.nindex == NULL) || (g.nlist == NULL) || (g.eweight == NULL)) { fprintf(stderr, "ERROR: memory allocation failed\n\n");  exit(-1); }

	cnt = fread(g.nindex, sizeof(g.nindex[0]), g.nodes + 1, f);  if (cnt != g.nodes + 1) { fprintf(stderr, "ERROR: failed to read neighbor index list\n\n");  exit(-1); }
	cnt = fread(g.nlist, sizeof(g.nlist[0]), g.edges, f);  if (cnt != g.edges) { fprintf(stderr, "ERROR: failed to read neighbor list\n\n");  exit(-1); }
	cnt = fread(g.eweight, sizeof(g.eweight[0]), g.edges, f);
	if (cnt == 0) {
		free(g.eweight);
		g.eweight = NULL;
	}
	else {
		if (cnt != g.edges) { fprintf(stderr, "ERROR: failed to read edge weights\n\n");  exit(-1); }
	}
	fclose(f);

	return g;
}

形式は圧縮隣接行列？だと思うのですがどのように書けばいいのでしょうか

行動規範の内容に同意します

回答1件

ベストアンサー

C++
1#include <cstdio>   // fopen, fclose, fread, fwrite, printf, putchar
2#include <cstdlib>  // exit
3using namespace std;
4
5struct Graph {
6	int nodes;
7	int edges;
8	int *nindex;
9	int *nlist;
10	int *eweight;
11};
12
13Graph readGraph(const char *const fname)
14{
15	Graph g;
16	int cnt;
17
18	FILE *f = fopen(fname, "rb");
19	if (f == NULL) {
20		fprintf(stderr, "ERROR: could not open file %s\n\n", fname);
21		exit(-1);
22	}
23	cnt = fread(&g.nodes, sizeof(g.nodes), 1, f);
24	if (cnt != 1) {
25		fprintf(stderr, "ERROR: failed to read nodes\n\n");
26		exit(-1);
27	}
28	cnt = fread(&g.edges, sizeof(g.edges), 1, f);
29	if (cnt != 1) {
30		fprintf(stderr, "ERROR: failed to read edges\n\n");
31		exit(-1);
32	}
33	if ((g.nodes < 1) || (g.edges < 0)) {
34		fprintf(stderr, "ERROR: node or edge count too low\n\n");
35		exit(-1);
36	}
37
38	g.nindex = (int *) malloc((g.nodes + 1) * sizeof(g.nindex[0]));
39	g.nlist = (int *) malloc(g.edges * sizeof(g.nlist[0]));
40	g.eweight = (int *) malloc(g.edges * sizeof(g.eweight[0]));
41	if ((g.nindex == NULL) || (g.nlist == NULL) || (g.eweight == NULL)) {
42		fprintf(stderr, "ERROR: memory allocation failed\n\n");
43		exit(-1);
44	}
45
46	cnt = fread(g.nindex, sizeof(g.nindex[0]), g.nodes + 1, f);
47	if (cnt != g.nodes + 1) {
48		fprintf(stderr, "ERROR: failed to read neighbor index list\n\n");
49		exit(-1);
50	}
51	cnt = fread(g.nlist, sizeof(g.nlist[0]), g.edges, f);
52	if (cnt != g.edges) {
53		fprintf(stderr, "ERROR: failed to read neighbor list\n\n");
54		exit(-1);
55	}
56	cnt = fread(g.eweight, sizeof(g.eweight[0]), g.edges, f);
57	if (cnt == 0) {
58		free(g.eweight);
59		g.eweight = NULL;
60	} else {
61		if (cnt != g.edges) {
62			fprintf(stderr, "ERROR: failed to read edge weights\n\n");
63			exit(-1);
64		}
65	}
66	fclose(f);
67
68	return g;
69}
70
71void writeGraph(const Graph *g, const char *fname)
72{
73	if ((g->nodes < 1) || (g->edges < 0)) {
74		fprintf(stderr, "ERROR: node or edge count too low\n\n");
75		exit(-1);
76	}
77	FILE *f = fopen(fname, "wb");
78	if (f == NULL) {
79		fprintf(stderr, "ERROR: could not create file %s\n\n", fname);
80		exit(-1);
81	}
82	int cnt = fwrite(&g->nodes, sizeof(g->nodes), 1, f);
83	if (cnt != 1) {
84		fprintf(stderr, "ERROR: failed to write nodes\n\n");
85		exit(-1);
86	}
87	cnt = fwrite(&g->edges, sizeof(g->edges), 1, f);
88	if (cnt != 1) {
89		fprintf(stderr, "ERROR: failed to write edges\n\n");
90		exit(-1);
91	}
92
93	cnt = fwrite(g->nindex, sizeof(g->nindex[0]), g->nodes + 1, f);
94	if (cnt != g->nodes + 1) {
95		fprintf(stderr, "ERROR: failed to write neighbor index list\n\n");
96		exit(-1);
97	}
98	cnt = fwrite(g->nlist, sizeof(g->nlist[0]), g->edges, f);
99	if (cnt != g->edges) {
100		fprintf(stderr, "ERROR: failed to write neighbor list\n\n");
101		exit(-1);
102	}
103	cnt = fwrite(g->eweight, sizeof(g->eweight[0]), g->edges, f);
104	if (cnt != g->edges) {
105		fprintf(stderr, "ERROR: failed to write edge weights\n\n");
106		exit(-1);
107	}
108	fclose(f);
109}
110
111int main()
112{
113	int index[4] = { 1, 2, 3, 4 };
114	int list[5] = { 5, 6, 7, 8, 9 };
115	int weight[5] = { 10, 11, 12, 13, 14 };
116
117	Graph g, g2;
118	g.nodes = 4 - 1; g.edges = 5;
119	g.nindex = index; g.nlist = list; g.eweight = weight;
120
121	writeGraph(&g, "graph.data");
122	g2 = readGraph("graph.data");
123
124	for (int i = 0; i <= g2.nodes; i++) printf(" %d", g2.nindex[i]);
125	putchar('\n');
126	for (int i = 0; i < g2.edges; i++) printf(" %d", g2.nlist[i]);
127	putchar('\n');
128	for (int i = 0; i < g2.edges; i++) printf(" %d", g2.eweight[i]);
129	putchar('\n');
130}