source: research/2008-displacement/vote.c @ 3033 Tweet

/* Quick voting software.
 * Usage: 
 *   vote <file1> <file2> ...
 * File format:
 *   <key1> <value1>
 *   <key1> <value1>
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define MAXLEN 20
#define MAXITEMS 2000

static char *items[MAXITEMS];
static int nitems;

static int *matrix;

static int lookup(char const *str)
{
    int i;

    for(i = 0; i < nitems; i++)
        if(!strcmp(str, items[i]))
            return i;

    return -1;
}

static int record(char const *str)
{
    int n = lookup(str);

    if(n >= 0)
        return n;

    items[nitems] = strdup(str);
    return nitems++;
}

static void recordfile(char const *file)
{
    char buf[MAXLEN];
    FILE *f;
    float val;

    f = fopen(file, "r");
    if(!f)
        return;
    while(!feof(f))
    {
        fscanf(f, "%s %g", buf, &val);
        record(buf);
    }
    fclose(f);
}

static void readfile(char const *file)
{
    float values[MAXITEMS];
    char buf[MAXLEN];
    FILE *f;
    float val;
    int n, i, j;

    for(i = 0; i < nitems; i++)
        values[i] = 9999.;

    f = fopen(file, "r");
    if(!f)
        return;
    while(!feof(f))
    {
        fscanf(f, "%s %g", buf, &val);
        n = lookup(buf);
        values[n] = val;
    }
    fclose(f);

    for(j = 0; j < nitems; j++)
        for(i = j + 1; i < nitems; i++)
            if(values[i] < values[j])
                matrix[j * nitems + i]++;
            else if(values[i] > values[j])
                matrix[i * nitems + j]++;
}

static void solvematrix(void)
{
    int wins[MAXITEMS];
    int i, j;

    memset(wins, 0, MAXITEMS * sizeof(int));

    for(j = 0; j < nitems; j++)
        for(i = j + 1; i < nitems; i++)
        {
            if(matrix[j * nitems + i] > matrix[i * nitems + j])
                wins[i]++;
            else
                wins[j]++;
        }

    for(i = 0; i < nitems; i++)
        printf("%s (%i): %i wins\n", items[i], i, wins[i]);
}

int main(int argc, char *argv[])
{
    int i;

    for(i = 1; i < argc; i++)
        recordfile(argv[i]);

    matrix = malloc(nitems * nitems * sizeof(int));
    memset(matrix, 0, nitems * nitems * sizeof(int));

    for(i = 1; i < argc; i++)
        readfile(argv[i]);

    solvematrix();

    return 0;
}