shailpatels.me
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day 1, part 2
+31
-13
1/main.c
+31
-13
1/main.c
···
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-
shail@debian13:~/Coding/advent_of_code_2025/1$ cat main.c
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#include <stdint.h>
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#include <stdio.h>
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#include <assert.h>
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#include <string.h>
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#include <stdlib.h>
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int circular_mod(const int x);
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typedef struct Lock {
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int position; //0-99
···
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l->zero_count = 0;
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}
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void Lock_rotate(Lock* lock, char direction, int distance) {
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lock->position = (direction == 'L') ?
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circular_mod(lock->position - distance) :
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circular_mod(lock->position + distance);
···
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lock->zero_count += 1;
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}
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int circular_mod(const int x) {
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int result = x % 100;
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if (result < 0) {
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result += 100;
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}
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return result;
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}
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int main(int argc, char ** argv) {
···
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FILE *file = fopen(argv[1], "r");
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assert(file != NULL);
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Lock lock;
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Lock_init(&lock);
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static const int LINE_BUFFER = 6;
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char line[LINE_BUFFER];
···
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const int distance = atoi(line + 1);
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assert(direction == 'L' || direction == 'R');
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Lock_rotate(&lock, direction, distance);
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}
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fclose(file);
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printf("Part 1: %d\n", lock.zero_count);
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}
···
1
#include <stdint.h>
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#include <stdio.h>
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#include <assert.h>
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#include <string.h>
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#include <stdlib.h>
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+
int circular_mod(const int x) {
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int result = x % 100;
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if (result < 0) {
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result += 100;
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}
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+
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return result;
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}
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typedef struct Lock {
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int position; //0-99
···
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l->zero_count = 0;
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}
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void Lock_rotate(Lock* lock, const char direction, const int distance) {
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lock->position = (direction == 'L') ?
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circular_mod(lock->position - distance) :
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circular_mod(lock->position + distance);
···
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lock->zero_count += 1;
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}
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void Lock_rotate_p2(Lock* lock, const char direction, const int distance) {
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int zeros_count = 0;
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+
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if (direction == 'L') {
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zeros_count = distance / 100;
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if (lock->position > 0 && distance % 100 >= lock->position)
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zeros_count++;
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+
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lock->position = circular_mod(lock->position - distance);
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} else {
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zeros_count = (distance + lock->position) / 100;
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lock->position = circular_mod(lock->position + distance);
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}
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+
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lock->zero_count += zeros_count;
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}
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int main(int argc, char ** argv) {
···
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FILE *file = fopen(argv[1], "r");
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assert(file != NULL);
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Lock lock_1, lock_2;
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Lock_init(&lock_1);
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Lock_init(&lock_2);
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static const int LINE_BUFFER = 6;
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char line[LINE_BUFFER];
···
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const int distance = atoi(line + 1);
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assert(direction == 'L' || direction == 'R');
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Lock_rotate(&lock_1, direction, distance);
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Lock_rotate_p2(&lock_2, direction, distance);
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}
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fclose(file);
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printf("Part 1: %d\n", lock_1.zero_count);
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printf("Part 2: %d\n", lock_2.zero_count);
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}