Nested boxes: what am I missing? - arrays

Question

I have to create an efficient program in C(99) where I have n boxes and I can insert one of them into another one (of the same n boxes), like a matryoshka. The goal is to find the maximum number of boxes that can be insereted and list them from the outside one to the most inside one (including the outside one). So, given x (width), y (height) and z (depth), all >= 0, a box can be inserted into another if x[i] < x[j] and y[i] < y[j] and z[i] < z[j] where i and j are the indexes (starting from 0) of two boxes. Boxes can't be rotated!.
The input file has this structure:
x[0] y[0] z[0]
…
x[n-1] y[n-1] z[n-1]
This is what I could achieve in some days of work:
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
typedef struct Array Boxes;
struct Array {
unsigned int count;
struct Box **elements;
};
struct Box {
int id;
double x;
double y;
double z;
struct Array inside;
};
int n;
/**
* Pretty print the boxes, according to the resulting output format
*
* #param boxes
*/
void print_boxes(Boxes boxes) {
printf("%d boxes\n", boxes.count);
for (int i = 0; i < boxes.count; ++i) {
struct Box box = *(boxes.elements[i]);
printf("box %d: %f %f %f - How many inside? %d\n", box.id, box.x, box.y, box.z, box.inside.count);
}
}
/**
* Append a box to an array
*
* #param arr
* #param box
* #param mem_alloc if true, memory will be allocated before appending the new box
*/
void array_append(struct Array *arr, struct Box *box, bool mem_alloc) {
if (mem_alloc) {
if (arr->count == 0) {
arr->elements = malloc(sizeof(struct Box *));
} else {
arr->elements = reallocarray(arr->elements, arr->count + 1, sizeof(struct Box *));
}
}
arr->elements[arr->count] = box;
arr->count += 1;
}
struct Array find_inside_boxes(Boxes boxes, struct Box *box) {
struct Array boxes_inside = {0, malloc(boxes.count * sizeof(struct Box *))};
for (int i = 0; i < boxes.count; ++i) {
struct Box *b = boxes.elements[i];
if (b->x < box->x && b->y < box->y && b->z < box->z) {
array_append(&boxes_inside, b, false);
}
}
return boxes_inside;
}
struct Box *find_best_box(Boxes boxes) {
struct Box *max = boxes.elements[0];
for (int i = 1; i < boxes.count; ++i) {
struct Box *box = boxes.elements[i];
if (box->inside.count > max->inside.count) {
max = box;
}
}
return max;
}
void print_inside_boxes(struct Box *box) {
Boxes boxes = {0, NULL};
array_append(&boxes, box, true);
while (box->inside.count > 0) {
box = find_best_box(box->inside);
array_append(&boxes, box, true);
}
print_boxes(boxes);
}
int main(int argc, char *argv[]) {
FILE *file = fopen(argv[1], "r");
if (!file) {
printf("No input or can't open the input file");
return EXIT_FAILURE;
}
fscanf(file, "%d\n", &n);
double x, y, z;
Boxes boxes = {n, malloc(n * sizeof(struct Box))};
for (int i = 0; fscanf(file, "%lf%lf%lf", &x, &y, &z) != EOF; i++) {
struct Box *box = malloc(sizeof(struct Box));
box->id = i;
box->x = x;
box->y = y;
box->z = z;
boxes.elements[i] = box;
}
fclose(file);
for (int i = 0; i < boxes.count; ++i) {
struct Box *box = boxes.elements[i];
box->inside = find_inside_boxes(boxes, box);
}
struct Box *best = find_best_box(boxes);
print_inside_boxes(best);
return EXIT_SUCCESS;
}
Basically, it gets the maximum box by its volume and it repeats this until there are no more boxes. Boxes are deleted from the boxes array if their dimensions (x, y, z) are incompatible with the latest box found.
This code mostly works. The issue is that it doesn't work with the last test file I have. I have these test files (.in files are input files, where .out are the expected outputs):
Sample 1: Input - Output
Sample 2: Input - Output
Sample 3: Input - Output
The program works with samples 1 and 2 (the first sample output differs for one line which is fine if the number of the boxes is valid and listed boxes follow the inserting condition). What doesn't work is sample 3: the program finds less boxes than the expected ones (my program finds the first board as 730 while the expected output is 714). What am I missing or what is wrong in my code? Can you help me to fix it, since I have little time left to deliver this.
Thanks to anyone who tries to help me!