111 lines
2.8 KiB
C
111 lines
2.8 KiB
C
/* For a number written in Roman numerals to be considered valid there are basic rules which must be followed.
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* Even though the rules allow some numbers to be expressed in more than one way there is always a "best" way of writing a particular number.
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*
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* For example, it would appear that there are at least six ways of writing the number sixteen:
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*
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* IIIIIIIIIIIIIIII
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* VIIIIIIIIIII
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* VVIIIIII
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* XIIIIII
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* VVVI
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* XVI
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*
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* However, according to the rules only XIIIIII and XVI are valid, and the last example is considered to be the most efficient,
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* as it uses the least number of numerals.
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* The 11K text file, roman.txt contains one thousand numbers written in valid, but not necessarily minimal, Roman numerals;
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* see About... Roman Numerals for the definitive rules for this problem.
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*
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* Find the number of characters saved by writing each of these in their minimal form.
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*
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* Note: You can assume that all the Roman numerals in the file contain no more than four consecutive identical units.*/
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#define _POSIX_C_SOURCE 199309L
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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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int reduce(char *numeral, int l);
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int main(int argc, char **argv)
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{
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int i, l, count = 0, count_reduced = 0;
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char *numerals[1000];
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double elapsed;
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struct timespec start, end;
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FILE *fp;
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clock_gettime(CLOCK_MONOTONIC, &start);
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if((fp = fopen("roman.txt", "r")) == NULL)
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{
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fprintf(stderr, "Error while opening file %s\n", "roman.txt");
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return 1;
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}
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/* Get the roman numerals from file, for each find its length, then
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* reduce it and find the new length. At the end, find the difference
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* of the two lengths.*/
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for(i = 0; i < 1000; i++)
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{
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fscanf(fp, "%ms", &numerals[i]);
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l = strlen(numerals[i]);
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count += l;
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l = reduce(numerals[i], l);
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count_reduced += l;
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free(numerals[i]);
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}
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fclose(fp);
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clock_gettime(CLOCK_MONOTONIC, &end);
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elapsed = (end.tv_sec - start.tv_sec) + (double)(end.tv_nsec - start.tv_nsec) / 1000000000;
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printf("Project Euler, Problem 89\n");
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printf("Answer: %d\n", count-count_reduced);
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printf("Elapsed time: %.9lf seconds\n", elapsed);
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return 0;
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}
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int reduce(char *numeral, int l)
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{
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/* DCCCC = CM.*/
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if(strstr(numeral, "DCCCC") != NULL)
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{
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l -= 3;
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}
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/* CCCC = CD.*/
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else if(strstr(numeral, "CCCC") != NULL)
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{
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l -= 2;
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}
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/* LXXXX = XC.*/
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if(strstr(numeral, "LXXXX") != NULL)
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{
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l -= 3;
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}
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/* XXXX = XL.*/
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else if(strstr(numeral, "XXXX") != NULL)
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{
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l -= 2;
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}
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/* VIIII = IX.*/
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if(strstr(numeral, "VIIII") != NULL)
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{
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l -= 3;
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}
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/* IIII = IV.*/
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else if(strstr(numeral, "IIII") != NULL)
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{
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l -= 2;
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}
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return l;
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}
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