123 lines
2.6 KiB
C
123 lines
2.6 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#define GRID_SIZE 50
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typedef struct point {
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int x, y;
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} point_t;
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typedef struct lots_of_points {
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point_t points[4];
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unsigned char index;
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} lots_of_points_t;
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int main(void) {
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FILE *fp = fopen("input", "r");
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if (fp == NULL) {
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perror("input");
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return 1;
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}
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char antinodes[GRID_SIZE][GRID_SIZE] = {0};
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lots_of_points_t data['z' + 1] = {0};
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for (unsigned int i = 0; i < GRID_SIZE; i++) {
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unsigned char buffer[GRID_SIZE] = {0};
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size_t read = fread(&buffer, sizeof(char), GRID_SIZE, fp);
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if (read == 0) {
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fprintf(stderr, "oopsy daisy\n");
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fclose(fp);
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return 1;
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}
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// move past the newline
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fseek(fp, 1, SEEK_CUR);
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for (unsigned int j = 0; j < GRID_SIZE; j++) {
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const unsigned char freq = buffer[j];
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if (freq != '.') {
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const point_t point = {(int)j, (int)i};
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data[freq].points[data[freq].index] = point;
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data[freq].index++;
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}
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}
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}
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unsigned int sum = 0;
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for (unsigned int i = 0; i < 'z' + 1; i++) {
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if (data[i].index == 0) {
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continue;
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}
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for (unsigned int j = 0; j < data[i].index; j++) {
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const point_t point = data[i].points[j];
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for (unsigned int k = 0; k < data[i].index; k++) {
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if (j == k) {
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continue;
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}
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const point_t other_point = data[i].points[k];
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for (int l = 0;; l++) {
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const int dist_x = point.x - other_point.x;
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const int dist_y = point.y - other_point.y;
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const point_t antinode = {point.x + dist_x * l, point.y + dist_y * l};
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if (antinode.x >= GRID_SIZE || antinode.x < 0 ||
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antinode.y >= GRID_SIZE || antinode.y < 0) {
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break;
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}
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if (antinodes[antinode.y][antinode.x] == 1) {
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continue;
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}
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antinodes[antinode.y][antinode.x] = 1;
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sum++;
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}
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}
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}
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}
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#ifdef DEBUG
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for (unsigned int i = 0; i < GRID_SIZE; i++) {
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for (unsigned int j = 0; j < GRID_SIZE; j++) {
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unsigned char found_freq = 0;
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for (unsigned int k = 0; k < 'z' + 1; k++) {
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for (unsigned int l = 0; l < data[k].index; l++) {
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if (data[k].points[l].x == j && data[k].points[l].y == i) {
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printf("%c", k);
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found_freq = 1;
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break;
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}
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}
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if (found_freq) {
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break;
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}
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}
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if (!found_freq) {
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if (antinodes[i][j] == 1) {
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printf("#");
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continue;
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}
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printf(".");
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}
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}
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printf("\n");
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}
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#endif
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printf("%u\n", sum);
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fclose(fp);
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return 0;
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}
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