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added stdint.h for fixed width ints

This commit is contained in:
Krishna Vedala 2020-04-07 00:41:14 -04:00
parent 6a09ade47d
commit 860b1fd501
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GPG Key ID: BA19ACF8FC8792F7
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 <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 num_digits = 4;
@ -12,15 +13,15 @@ int main(int argc, char* argv[])
int64_t prod = 1, max_prod = 0;
/* 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
*/
if (argc == 2)
num_digits = atoi(argv[1]);
/* allocate memory to store past values */
buffer = calloc(num_digits, sizeof(uint8_t));
if(!buffer)
if (!buffer)
{
perror("Unable to allocate memory for buffer");
return -1;
@ -31,57 +32,58 @@ int main(int argc, char* argv[])
if (!fp)
{
perror("Unable to open file");
free(buffer); /* free allocated memory */
free(buffer); /* free allocated memory */
return -1;
}
/* loop through all digits in the file */
do
do
{
/* get character from file */
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
*/
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;
} 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 */
}
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 */
/* left shift the buffer -
* 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++)
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)
{
/* 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
*/
prod /= num_prev; /* divide first to avoid over-flows */
prod /= num_prev; /* divide first to avoid over-flows */
prod *= num;
}
else
{
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;
break; /* break innermost for-loop */
break; /* break innermost for-loop */
}
prod *= buffer[i];
}
@ -93,14 +95,14 @@ int main(int argc, char* argv[])
max_prod = prod;
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);
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 */
for (; num_digits > 0; num_digits--)
{
char ch = getc(fp); /* get character */
char ch = getc(fp); /* get character */
/* skip invalid character */
if (ch < 0x30 || ch > 0x39)
continue;
@ -110,8 +112,8 @@ int main(int argc, char* argv[])
printf("%c = %lld\n", ch, max_prod);
}
fclose(fp); /* close file */
free(buffer); /* free allocated memory */
fclose(fp); /* close file */
free(buffer); /* free allocated memory */
return 0;
}