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#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define COUNT(a) ((int)(sizeof(a) / sizeof 0 [a]))
#define WHOLE \
fseek(fp, 0, SEEK_END); \
long fsize = ftell(fp); \
fseek(fp, 0, SEEK_SET); \
char *data = malloc(fsize + 1); \
fread(data, 1, fsize, fp); \
data[fsize] = 0;
struct node {
int x, y;
int risk;
};
// prioritized queue
struct queue {
struct node *heap;
int size, max;
};
static void pop(struct queue *queue, struct node *out)
{
if (queue->size <= 0) {
fprintf(stderr, "Can't pop null node\n");
exit(1);
}
*out = queue->heap[0];
queue->heap[0] = queue->heap[--queue->size];
for (int i = 0, curr = 0;; curr = i) {
int child = (curr << 1) + 1;
if (child < queue->size && queue->heap[child].risk < queue->heap[curr].risk)
i = child;
child++;
if (child < queue->size && queue->heap[child].risk < queue->heap[i].risk)
i = child;
if (i == curr)
break;
struct node temp = queue->heap[curr];
queue->heap[curr] = queue->heap[i];
queue->heap[i] = temp;
}
}
static void push(struct queue *queue, int x, int y, int risk)
{
if (queue->size >= queue->max) {
fprintf(stderr, "Queue size too big\n");
exit(1);
}
queue->heap[queue->size].x = x;
queue->heap[queue->size].y = y;
queue->heap[queue->size].risk = risk;
int p = 0;
for (int i = queue->size++; i > 0; i = p) {
p = (i - 1) >> 1;
if (queue->heap[p].risk <= queue->heap[i].risk)
break;
// Swap
struct node temp = queue->heap[i];
queue->heap[i] = queue->heap[p];
queue->heap[p] = temp;
}
}
static struct queue *create(int size)
{
struct queue *queue = malloc(sizeof(*queue));
queue->heap = malloc(sizeof(*queue->heap) * size);
queue->size = 0;
queue->max = size;
return queue;
}
#define SIZE 100
#define GET(x, y) (data[(y) * (SIZE + 1) + (x)] - '0')
static int part_one(FILE *fp)
{
int risk = 0;
WHOLE;
int visited[SIZE][SIZE] = { 0 };
struct queue *queue = create(1000);
push(queue, 0, 0, 0);
while (1) {
struct node node;
pop(queue, &node);
int x = node.x;
int y = node.y;
risk = node.risk;
if (visited[x][y])
continue;
if (x == SIZE - 1 && y == SIZE - 1)
break;
visited[x][y] = 1;
if (x + 1 < SIZE && !visited[x + 1][y])
push(queue, x + 1, y, risk + GET(x + 1, y));
if (y + 1 < SIZE && !visited[x][y + 1])
push(queue, x, y + 1, risk + GET(x, y + 1));
if (x - 1 >= 0 && !visited[x - 1][y])
push(queue, x - 1, y, risk + GET(x - 1, y));
if (y - 1 >= 0 && !visited[x][y - 1])
push(queue, x, y - 1, risk + GET(x, y - 1));
}
free(data);
free(queue->heap);
free(queue);
return risk;
}
#define SIZE2 (SIZE * 5)
#define GET2(x, y) \
(((data[((y) % SIZE) * (SIZE + 1) + ((x) % SIZE)] - '0' + ((x) / SIZE + (y) / SIZE)) - \
1) % 9 + \
1)
static int part_two(FILE *fp)
{
int risk = 0;
WHOLE;
int visited[SIZE2][SIZE2] = { 0 };
struct queue *queue = create(10000);
push(queue, 0, 0, 0);
while (1) {
struct node node;
pop(queue, &node);
int x = node.x;
int y = node.y;
risk = node.risk;
if (visited[x][y])
continue;
if (x == SIZE2 - 1 && y == SIZE2 - 1)
break;
visited[x][y] = 1;
if (x + 1 < SIZE2 && !visited[x + 1][y])
push(queue, x + 1, y, risk + GET2(x + 1, y));
if (y + 1 < SIZE2 && !visited[x][y + 1])
push(queue, x, y + 1, risk + GET2(x, y + 1));
if (x - 1 >= 0 && !visited[x - 1][y])
push(queue, x - 1, y, risk + GET2(x - 1, y));
if (y - 1 >= 0 && !visited[x][y - 1])
push(queue, x, y - 1, risk + GET2(x, y - 1));
}
free(data);
free(queue->heap);
free(queue);
return risk;
}
int main(int argc, char *argv[])
{
(void)argc;
(void)argv;
FILE *fp = fopen("input", "r");
if (!fp)
exit(EXIT_FAILURE);
clock_t tic = clock();
printf("%d\n", part_one(fp));
rewind(fp);
printf("%d\n", part_two(fp));
clock_t toc = clock();
printf("TIME: %f seconds\n", (double)(toc - tic) / CLOCKS_PER_SEC);
fclose(fp);
return 0;
}
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