109 lines
2.8 KiB
C
109 lines
2.8 KiB
C
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#include <math.h>
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#include <stdlib.h>
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#include <stdio.h>
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static int cmp_uint(const void* p1, const void* p2)
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{
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const uint a = *(const uint*)p1;
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const uint b = *(const uint*)p2;
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if (a < b)
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return -1;
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if (a == b)
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return 0;
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return 1;
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}
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int main(void)
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{
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const uint LIMIT = 50000000;
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uint* const prime_numbers = malloc(4096);
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if (prime_numbers == NULL)
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{
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perror("Failed to allocate memory for prime numbers");
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return EXIT_FAILURE;
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}
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uint* const prime_numbers_end = prime_numbers + 4096 / sizeof(*prime_numbers);
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uint max_pn = (uint)sqrt(LIMIT);
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prime_numbers[0] = 2u;
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prime_numbers[1] = 3u;
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uint* next_pn = &prime_numbers[2];
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for (uint num = *(next_pn - 1) + 2; num <= max_pn; num += 2)
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{
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for (uint i = (uint)sqrt(num); i >= 3; --i)
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{
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if (num % i == 0)
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goto next;
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}
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if (next_pn >= prime_numbers_end)
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{
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fprintf(stderr, "Memory for prime numbers exceeded, but more needed.\n");
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return EXIT_FAILURE;
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}
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*next_pn++ = num;
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next:
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;
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}
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printf("There are %ld numbers below sqrt(50.000.000)\n", next_pn - prime_numbers);
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uint* nums = NULL;
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uint* nums_end = nums;
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uint* next_num = nums;
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for (uint* pn2 = prime_numbers; pn2 < next_pn; ++pn2)
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{
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uint pow2 = *pn2 * *pn2;
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for (uint* pn3 = prime_numbers; pn3 < next_pn; ++pn3)
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{
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uint pow3 = *pn3 * *pn3 * *pn3;
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uint sum = pow2 + pow3;
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if (sum >= LIMIT)
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break;
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for (uint* pn4 = prime_numbers; pn4 < next_pn; ++pn4)
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{
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uint pow4 = *pn4 * *pn4;
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pow4 *= pow4;
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uint sum2 = sum + pow4;
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if (sum2 >= LIMIT)
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break;
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if (next_num >= nums_end)
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{
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long next_num_idx = next_num - nums;
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size_t new_size = (uint)(nums_end - nums) * sizeof(*nums) + (1 << 20);
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nums = realloc(nums, new_size);
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if (nums == NULL)
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{
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perror("Failed to increase memory for result numbers");
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return EXIT_FAILURE;
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}
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nums_end = nums + new_size / sizeof(*nums);
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next_num = &nums[next_num_idx];
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}
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*next_num++ = sum2;
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}
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}
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}
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nums_end = next_num;
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qsort(nums, (size_t)(nums_end - nums), sizeof(*nums), cmp_uint);
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uint count = 1;
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for (const uint* n = nums + 1; n < nums_end; ++n)
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if (*(n - 1) != *n)
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++count;
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printf("Answer: %d\n", count);
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return EXIT_SUCCESS;
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}
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