numbers.c

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>

#define LOG_2 0x02000000
#define LOG_3 0x032B8034
#define LOG_5 0x04A4D3C2
#define LOG_7 0x059D5D9F
#define LOG_LIMIT 0x80000000
#define COUNT 85348

static unsigned long long numbers[COUNT];

static int comparelongs(const void *a, const void *b)
{
	if ((*(unsigned long long*)a) > (*(unsigned long long*)b)) {
		return 1;
	}

	if ((*(unsigned long long*)a) < (*(unsigned long long*)b)) {
		return -1;
	}

	return 0;
}

static void initialize(unsigned long long *array)
{
	unsigned l2, l3, l5, l7, count;
	unsigned long long x2, x3, x5, x7;

	for (
		l2 = 0, x2 = 1, count = 0;
		l2 < LOG_LIMIT;
		l2 += LOG_2, x2 *= 2
	) {

		for (
			l3 = l2, x3 = x2;
			l3 < LOG_LIMIT;
			l3 += LOG_3, x3 *= 3
		) {

			for (
				l5 = l3, x5 = x3;
				l5 < LOG_LIMIT;
				l5 += LOG_5, x5 *= 5
			) {

				for (
					l7 = l5, x7 = x5;
					l7 < LOG_LIMIT;
					l7 += LOG_7, x7 *= 7
				) {

					assert(count < COUNT);

					array[count] = x7;
					++count;

				}
			}
		}
	}

	assert(count == COUNT);

	qsort(array, count, sizeof(*array), comparelongs);
}

unsigned long long find(unsigned long long x)
{
	int a = 0, b = COUNT;

	do {
		int c = (a + b) / 2;
		if (numbers[c] > x) {
			b = c;
		} else {
			a = c;
		}
	} while (b - a > 1);

	return numbers[a] > x ? numbers[a] : numbers[b];
}

int main(int argc, char *argv[])
{
	if (argc < 2) {
		exit(EXIT_FAILURE);
	}

	initialize(numbers);

	int i;

	for (i = 1; i < argc; ++i) {
		unsigned long long x = atoll(argv[i]);
		printf("%Lu %Lu\n", x, find(x));
	}
}