/* Using names.txt, a 46K text file containing over five-thousand first names, begin by sorting it into alphabetical order.
 * Then working out the alphabetical value for each name, multiply this value by its alphabetical position in the list to obtain a name score.
 *
 * For example, when the list is sorted into alphabetical order, COLIN, which is worth 3 + 15 + 12 + 9 + 14 = 53, is the 938th name in the list.
 * So, COLIN would obtain a score of 938 × 53 = 49714.
 *
 * What is the total of all the name scores in the file?*/

#define _POSIX_C_SOURCE 199309L

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include "projecteuler.h"

int compare(void *string1, void *string2);

int main(int argc, char **argv)
{
    FILE *fp;
    int i, j, n, len, score, sum = 0;
    double elapsed;
    char *line, **names;
    struct timespec start, end;

    clock_gettime(CLOCK_MONOTONIC, &start);

    if((fp = fopen("names.txt", "r")) == NULL)
    {
        fprintf(stderr, "Error while opening file %s\n", "names.txt");
        return 1;
    }

    fscanf(fp, "%ms", &line);

    fclose(fp);

    len = strlen(line);
    n = 1;

    /* Count the names in the file.*/
    for(i = 0; i < len; i++)
    {
        if(line[i] == ',')
        {
            n++;
        }
    }

    if((names = (char **)malloc(n*sizeof(char *))) == NULL)
    {
        fprintf(stderr, "Error while allocating memory\n");
        return 1;
    }

    /* Save each name in a string.*/
    names[0] = strtok(line, ",\"");

    for(i = 1; i < n; i++)
    {
        names[i] = strtok(NULL, ",\"");
    }

    /* Use quick_sort algorithm implemented in projecteuler.c to sort the names.*/
    quick_sort((void **)names, 0, n-1, compare);

    /* Calculate the score of each name an multiply by its position.*/
    for(i = 0; i < n; i++)
    {
        len = strlen(names[i]);
        score = 0;
        for(j = 0; j < len; j++)
        {
            score += names[i][j] - 'A' + 1;
        }
        score *= (i + 1);
        sum += score;
    }

    free(line);

    clock_gettime(CLOCK_MONOTONIC, &end);

    elapsed = (end.tv_sec - start.tv_sec) + (double)(end.tv_nsec - start.tv_nsec) / 1000000000;

    printf("Project Euler, Problem 22\n");
    printf("Answer: %d\n", sum);
    printf("Elapsed time: %.9lf seconds\n", elapsed);

    return 0;
}

/* Function to compare two strings, to pass to the quick_sort function.*/
int compare(void *string1, void *string2)
{
    char *s1, *s2;

    s1 = (char *)string1;
    s2 = (char *)string2;

    return strcmp(s1, s2);
}