#include "aoc.h"
#include <stdlib.h>

typedef struct {
    i64 *data;
    isize len, cap;
} Ints;

static int
cmp_i64(const void *a, const void *b) {
    return *(i64 *)a - *(i64 *)b;
}

int main(int argc, char **argv) {
    Arena *arena = make_arena(Megabytes(1));
    Arena *temp = make_arena(Megabytes(1));

    Ints left = {0}, right = {0};

    Tokens lines = read_lines(arena, argv[1]);
    for (isize i = 0; i < lines.len; i++) {
        str line = lines.tokens[i];
        str fst, snd;
        str_split(line, STR(" "), &fst, &snd);

        *push(&left, arena)  = parse_i64(str_trim(fst), *temp);
        *push(&right, arena) = parse_i64(str_trim(snd), *temp);
    }

    // Part 1
    qsort(left.data, left.len, sizeof(i64), cmp_i64);
    qsort(right.data, right.len, sizeof(i64), cmp_i64);

    i64 part_1 = 0;
    ASSERT(left.len == right.len);
    for (isize i = 0; i < left.len; i++) {
        part_1 += labs(left.data[i] - right.data[i]);
    }
    printf("%ld\n", part_1);
    ASSERT(part_1 == 1223326);

    // Part 2
    i64 part_2 = 0;
    for (isize i = 0; i < left.len; i++) {
        i64 l = left.data[i], r = right.data[i];
        // count occurrences of `l` in `right`
        int occurrences = 0;
        // since arrays are sorted, only need to go up to value `l`
        for (isize j = 0; j < right.len && right.data[j] <= l; j++) {
            occurrences += (right.data[j] == l);
        }
        part_2 += l * occurrences;
    }
    printf("%ld\n", part_2);
    ASSERT(part_2 == 21070419);
}