OpenSoure_Repos/TheAlgorithms-C
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added stdint.h for fixed width ints

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Krishna Vedala 2020-04-07 00:41:14 -04:00
parent 6a09ade47d
commit 860b1fd501
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1 changed files with 29 additions and 27 deletions
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56
project_euler/Problem 08/sol2.c
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@ -1,8 +1,9 @@
#include <stdio.h> #include <stdio.h>
#include <stdlib.h> #include <stdlib.h>
#include <string.h> /* for memmove */ #include <stdint.h>
#include <string.h> /* for memmove */
int main(int argc, char* argv[]) int main(int argc, char *argv[])
{ {
int position = 0, num_bad_chars = 0; int position = 0, num_bad_chars = 0;
int num_digits = 4; int num_digits = 4;
@ -12,15 +13,15 @@ int main(int argc, char* argv[])
int64_t prod = 1, max_prod = 0; int64_t prod = 1, max_prod = 0;
/* if second command-line argument is given, /* if second command-line argument is given,
* use it as the number of digits to compute * use it as the number of digits to compute
* successive product for * successive product for
*/ */
if (argc == 2) if (argc == 2)
num_digits = atoi(argv[1]); num_digits = atoi(argv[1]);
/* allocate memory to store past values */ /* allocate memory to store past values */
buffer = calloc(num_digits, sizeof(uint8_t)); buffer = calloc(num_digits, sizeof(uint8_t));
if(!buffer) if (!buffer)
{ {
perror("Unable to allocate memory for buffer"); perror("Unable to allocate memory for buffer");
return -1; return -1;
@ -31,57 +32,58 @@ int main(int argc, char* argv[])
if (!fp) if (!fp)
{ {
perror("Unable to open file"); perror("Unable to open file");
free(buffer); /* free allocated memory */ free(buffer); /* free allocated memory */
return -1; return -1;
} }
/* loop through all digits in the file */ /* loop through all digits in the file */
do do
{ {
/* get character from file */ /* get character from file */
ch = getc(fp); ch = getc(fp);
/* the ASCII codes of digits is between 0x30 and 0x39. /* the ASCII codes of digits is between 0x30 and 0x39.
* any character not in this range implies an invalid character * any character not in this range implies an invalid character
*/ */
if (ch < 0x30 || ch > 0x39) if (ch < 0x30 || ch > 0x39)
{ {
num_bad_chars ++; /* this is used to get the bad characters in the sequence of 13 characters */ num_bad_chars++; /* this is used to get the bad characters in the sequence of 13 characters */
continue; continue;
} else if (num_bad_chars > 0) }
num_bad_chars --; else if (num_bad_chars > 0)
num_bad_chars--;
num = ch - 0x30; /* convert character digit to number */
num_prev = buffer[0]; /* previous n^th digit */ num = ch - 0x30; /* convert character digit to number */
num_prev = buffer[0]; /* previous n^th digit */
/* left shift the buffer - /* left shift the buffer -
* using a for loop or a faster memory move * using a for loop or a faster memory move
*/ */
memmove(buffer, buffer+1, num_digits-1); memmove(buffer, buffer + 1, num_digits - 1);
/* /*
for (int i = 1; i < num_digits; i++) for (int i = 1; i < num_digits; i++)
buffer[i-1] = buffer[i]; buffer[i-1] = buffer[i];
*/ */
buffer[num_digits-1] = num; /* save the latest number in buffer */ buffer[num_digits - 1] = num; /* save the latest number in buffer */
if (num_prev != 0) if (num_prev != 0)
{ {
/* since product is accumulated, the new product can be obtained by simply /* since product is accumulated, the new product can be obtained by simply
* multiplying the new digit and dividing with the oldest digit * multiplying the new digit and dividing with the oldest digit
*/ */
prod /= num_prev; /* divide first to avoid over-flows */ prod /= num_prev; /* divide first to avoid over-flows */
prod *= num; prod *= num;
} }
else else
{ {
prod = 1; prod = 1;
for(int i = 0; i < num_digits; i++) for (int i = 0; i < num_digits; i++)
{ {
if(buffer[i] == 0) if (buffer[i] == 0)
{ {
prod = 0; prod = 0;
break; /* break innermost for-loop */ break; /* break innermost for-loop */
} }
prod *= buffer[i]; prod *= buffer[i];
} }
@ -93,14 +95,14 @@ int main(int argc, char* argv[])
max_prod = prod; max_prod = prod;
position = ftell(fp) - num_bad_chars - num_digits - 1; position = ftell(fp) - num_bad_chars - num_digits - 1;
} }
} while(!feof(fp)); /* loop till end of file is reached */ } while (!feof(fp)); /* loop till end of file is reached */
printf("Maximum product: %lld\t Location: %d^th position\n\t", max_prod, position); printf("Maximum product: %lld\t Location: %d^th position\n\t", max_prod, position);
fseek(fp, position, SEEK_SET); /* move cursor to identified position in file */ fseek(fp, position, SEEK_SET); /* move cursor to identified position in file */
/* loop through all digits */ /* loop through all digits */
for (; num_digits > 0; num_digits--) for (; num_digits > 0; num_digits--)
{ {
char ch = getc(fp); /* get character */ char ch = getc(fp); /* get character */
/* skip invalid character */ /* skip invalid character */
if (ch < 0x30 || ch > 0x39) if (ch < 0x30 || ch > 0x39)
continue; continue;
@ -110,8 +112,8 @@ int main(int argc, char* argv[])
printf("%c = %lld\n", ch, max_prod); printf("%c = %lld\n", ch, max_prod);
} }
fclose(fp); /* close file */ fclose(fp); /* close file */
free(buffer); /* free allocated memory */ free(buffer); /* free allocated memory */
return 0; return 0;
} }