c - 如何生成一组数字

Question

我必须生成集合 Z满足方程 i = 2^a * 3^b 的前 100 个整数，与 a和b是整数。

即Z = {1, 2, 3, 4, 6, 8, 9, 12, ...}

我可以使用什么算法？我需要用 C 语言实现它。

Answer 1

用 C 语言

#include <stdio.h>
#include <math.h>
#include <stdint.h>
typedef unsigned long long int ull;

ull cmp(const void * a, const void * b) { return *(ull *)a  - *(ull *)b; } 

int main() {
    int i = 0, a, b;
    int A = 17, 
        B = 16;
    int MAX = A * B;
    ull z[MAX];
    for (b = 0; b < B; ++b) {
        for (a = 0; a < A; ++a) {
            if (i >= MAX) break;
            z[i++] = pow(2, a) * pow(3, b);
        }
    }
    qsort(z, MAX, sizeof(ull), cmp);
    printf("{ ");
    for (i = 0; i < 100; ++i)
        printf("%lld%c ", z[i], i < 99 ? ',' : 0);
    printf("}");
    return 0;
}

输出

{ 1, 2, 3, 4, 6, 8, 9, 12, 16, 18, 24, 27, 32, 36, 48, 54, 64, 72, 81, 96, 108, 128, 144, 162, 192, 216, 243, 256, 288, 324, 384, 432, 486, 512, 576, 648, 729, 768, 864, 972, 1024, 1152, 1296, 1458, 1536, 1728, 1944, 2048, 2187, 2304, 2592, 2916, 3072, 3456, 3888, 4096, 4374, 4608, 5184, 5832, 6144, 6561, 6912, 7776, 8192, 8748, 9216, 10368, 11664, 12288, 13122, 13824, 15552, 16384, 17496, 18432, 19683, 20736, 23328, 24576, 26244, 27648, 31104, 32768, 34992, 36864, 39366, 41472, 46656, 49152, 52488, 55296, 59049, 62208, 65536, 69984, 73728, 78732, 82944, 93312 }

编辑:现在提供正确的输出而不会溢出(请参阅 http://ideone.com/Rpbqms )