Advent-of-Code/2021/day12/solution-part2.c

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

#define ANSI_COLOR_RED     "\x1b[31m"
#define ANSI_COLOR_YELLOW  "\x1b[33m"
#define ANSI_COLOR_RESET   "\x1b[0m"

typedef struct VertexList VertexList;
typedef struct Vertex Vertex;

struct Vertex{
	char name[10];
	VertexList *adjacent;
	bool bigCave;
	unsigned int visited;
};

struct VertexList{
	Vertex *vertex;
	//This next pointer is to create a linked list of verticies, it does not reperesent graph position or adjacency
	VertexList *next;

};


void printVertexList(VertexList *start){
	VertexList *next = start;
	while (next != NULL){
		if ( next->vertex->bigCave ) printf(ANSI_COLOR_RED);
		printf("%s ",next->vertex->name);
		if ( next->vertex->bigCave ) printf(ANSI_COLOR_RESET);
		next=next->next;
	}
	printf("\n");
}

int indexOf(VertexList *first, char *name ){
	VertexList *current = first;
	for ( unsigned int count = 0; current != NULL; count++ ){
		if ( strcmp(current->vertex->name, name) == 0 ) return count;
		else current = current->next;
	}

	return -1;
}

Vertex* getVertex(VertexList *first, char name[20]){
	VertexList *current = first;
	while ( current != NULL ){
		if ( strcmp(current->vertex->name, name) == 0 ) return current->vertex;
		else current = current->next;
	}
	return NULL;
}

Vertex* newVertex(char name[20]){
	Vertex *new = (Vertex*)malloc(sizeof(Vertex));
	new->adjacent = NULL;
	new->visited = 0;
	new->bigCave = ( name[0] >= 'A' && name[0] <= 'Z' );
	strcpy(new->name,name);
	return new;
}

VertexList* newVertexListItem(Vertex *virtex){
	VertexList *newList = (VertexList*)malloc(sizeof(VertexList));
	newList->next = NULL;
	newList->vertex = virtex;
	return newList;
}

VertexList* getLast(VertexList *current){
	if ( current == NULL ) return NULL;
	while ( current->next != NULL ) current = current->next;
	return current;
}

unsigned int countPaths(Vertex *current, bool smallVisitedTwice){
	// This is the break for the recursion - when we reach the end
	if ( strcmp( current->name, "end" ) == 0 ) return 1;

	current->visited++;

	unsigned int count = 0;
	VertexList *toTry = current->adjacent;
	while ( toTry != NULL ){
		if ( toTry->vertex->bigCave || toTry->vertex->visited == 0 )
			count += countPaths(toTry->vertex, smallVisitedTwice);
		else if ( !smallVisitedTwice && toTry->vertex->visited < 2 && strcmp(toTry->vertex->name, "start") != 0 ) {
			count += countPaths(toTry->vertex, true);
		}

		toTry = toTry->next;
	}


	current->visited--;
	return count;
}

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

		VertexList *firstVirtex = NULL;
		VertexList *lastVertex = getLast(firstVirtex);

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

		if ( fp == NULL ) {
			return 1;
		}

		char vertex1[20];
		char vertex2[20];
		char vertexStart[20] = "start";
		Vertex *v1, *v2;
		while ( !feof(fp) && fscanf( fp, "%[^-]-%s\n", vertex1,vertex2 )  ){
			//Ensures the first virtex exists
			v1 = getVertex(firstVirtex, vertex1);
			v2 = getVertex(firstVirtex, vertex2);
			if ( v1 == NULL ){
				v1 = newVertex(vertex1);
				if ( firstVirtex == NULL ){
					firstVirtex = newVertexListItem(v1);
					lastVertex = firstVirtex;
				} else {
					lastVertex->next = newVertexListItem(v1);
					lastVertex = lastVertex->next;
				}
			}
			//Ensures the second vertex exists
			if ( v2 == NULL ){
				v2 = newVertex(vertex2);
				lastVertex->next = newVertexListItem(v2);
				lastVertex = lastVertex->next;
			}

			//Links v1 and v2
			if ( v1->adjacent == NULL ){
				v1->adjacent = newVertexListItem(v2);
			} else if ( indexOf(v1->adjacent, v2->name) < 0 ) {
				getLast(v1->adjacent)->next = newVertexListItem(v2);
			}

			if ( v2->adjacent == NULL ){
				v2->adjacent = newVertexListItem(v1);
			} else if ( indexOf(v2->adjacent, v1->name) < 0 ) {
				getLast(v2->adjacent)->next = newVertexListItem(v1);
			}

			//break;
		}

		printVertexList(firstVirtex);

		printf("\n\nThere are %i valid paths", countPaths(getVertex(firstVirtex, vertexStart), false));

		fclose(fp);

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