Advent-of-Code/2021/day6/solution-part1.c

#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <stdlib.h>


typedef struct LanternFishListItem LanternFishListItem;
struct LanternFishListItem {
	unsigned int daysToSpawn;
	LanternFishListItem *next;
};

void printFrom( LanternFishListItem *first ){
	printf("%i,", first->daysToSpawn);
	if ( first->next != NULL ) printFrom(first->next);
}

unsigned int countFrom( LanternFishListItem *current ){
	unsigned int count = 1;
	while ( current->next != NULL ){
		count++;
		current = current->next;
	}
	return count;
}

int main( int argc, char *argv[] ){
	if( argc == 2 ) {


		FILE *fp=fopen(argv[1], "r");

		LanternFishListItem *first = NULL;
		LanternFishListItem *previous = NULL;
		unsigned int no;
		char ch;
		while ( fscanf( fp, "%i%c", &no, &ch ) ){

			LanternFishListItem *lf = (LanternFishListItem*)malloc(sizeof(LanternFishListItem));
			lf->next = NULL;
			lf->daysToSpawn = no;

			if ( first == NULL ){
				first = lf;
			} else {
				previous->next = lf;
			}

			previous = lf;

			if ( ch == '\n' ) break;
		}

		for ( unsigned int i = 0; i < 80; i++ ){
			unsigned int toAdd=0;
			LanternFishListItem *current = first;
			while (current != NULL){
				if ( current->daysToSpawn == 0 ){
					toAdd++;
					current->daysToSpawn = 7;
				}
				current->daysToSpawn--;
				if ( current->next != NULL )
					current = current->next;
				else
					break;

			}


			previous = current;
			//printf("On day %i add %i fish\n", i, toAdd);
			for (unsigned int j = 0; j < toAdd; j++){
				LanternFishListItem *lf = (LanternFishListItem*)malloc(sizeof(LanternFishListItem));
				lf->next = NULL;
				lf->daysToSpawn = 8;
				previous->next = lf;
				previous = lf;
			}

			//printf("After %3i day: ", i+1);
			//printFrom(first);
			//printf("\n");






		}
		printf("There are %i Fish.\n",countFrom(first));


		fclose(fp);



		return 0;
	} else {
		printf("You need to provide a file\n");
		return 1;
	}
}