mirror of https://github.com/TheAlgorithms/C
89 lines
2.4 KiB
C
89 lines
2.4 KiB
C
/**
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* \file
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* \brief [Problem 26](https://projecteuler.net/problem=26) solution
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* \author [Krishna Vedala](https://github.com/kvedala)
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#ifdef _OPENMP
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#include <omp.h>
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#endif
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#define MAX_DENO 2000 /**< limit of unit fractions */
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#define MAX_LEN \
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(MAX_DENO + 10) /**< length of resulting recurring fraction number */
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/** comparison function for use with internal `qsort` algorithm */
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int compare(const void *a, const void *b)
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{
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return (*(unsigned short *)a - *(unsigned short *)b);
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}
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/** Main function */
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int main(int argc, char *argv[])
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{
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unsigned short max_digits = 0, max_idx_number = 0;
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clock_t start_time = clock();
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short deno;
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#ifdef _OPENMP
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#pragma omp for
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#endif
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for (deno = 2; deno < MAX_DENO; deno++)
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{
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unsigned short remainders[MAX_LEN];
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unsigned short rem = 1, *rem_ptr = remainders;
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memset(remainders, (unsigned short)-1,
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MAX_LEN * sizeof(unsigned short));
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// remainders[0] = 1;
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// printf("1/%-4u\t ", deno);
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unsigned short index = 0, num_digits;
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while (rem != 0)
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{
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rem = (rem * 10) % deno;
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if (rem == 0)
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{
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index = 0;
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break;
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}
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rem_ptr = (unsigned short *)bsearch(
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&rem, remainders, MAX_LEN, sizeof(unsigned short), compare);
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// printf("%2d, ", rem);
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// printf("(%14p), ", rem_ptr);
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if (rem_ptr != NULL)
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break;
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remainders[index] = rem;
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rem_ptr = remainders;
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index++;
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}
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num_digits = index - (rem_ptr - remainders);
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// printf("\n\t(%14p, %14p, %4u, %4u)\n", rem_ptr, remainders, index,
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// num_digits);
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#ifdef _OPENMP
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#pragma omp critical
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{
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#endif
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if (num_digits > max_digits)
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{
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max_digits = num_digits;
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max_idx_number = deno;
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// printf("\t (%u, %u)\n ", max_digits, max_idx_number);
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}
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#ifdef _OPENMP
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}
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#endif
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}
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clock_t end_time = clock();
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printf("Time taken: %.4g ms\n",
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1e3 * (double)(end_time - start_time) / CLOCKS_PER_SEC);
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printf("Maximum digits: %hu\t Denominator: %hu\n", max_digits,
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max_idx_number);
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return 0;
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}
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