Advent-of-Code/2021/day10/solution-part2.c

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

int countLines(FILE *fp){
	long int lines =0;
	while (EOF != (fscanf(fp, "%*[^\n]"), fscanf(fp,"%*c")))
		++lines;
	return lines;
}

int cmp_asc_unsigned_long(const void *a, const void *b) {
    return *(unsigned long*)a > *(unsigned long*)b;
}

unsigned int getScore(char symbol){
	switch (symbol) {
		case ')':
			return 1;
			break;
		case ']':
			return 2;
			break;
		case '}':
			return 3;
			break;
		case '>':
			return 4;
			break;
		default:
			return 0;
			break;
	}
}

void corruptLine(char expected, char found, FILE *fp){
	fscanf(fp, "%*s");
}

int lineLength(FILE *fp){
	unsigned int lineLength=0;
	char ch = fgetc(fp);
	while ( ch != '\n' && ch != EOF ){
		lineLength++;
		ch = fgetc(fp);
		if ( lineLength > 30 ) break;
	}
	return lineLength;
}


char reverse(char ch){
	switch (ch) {
		case '[':
			return ']';
			break;
		case ']':
			return '[';
			break;
		case '(':
			return ')';
			break;
		case ')':
			return '(';
			break;
		case '{':
			return '}';
			break;
		case '}':
			return '{';
			break;
		case '<':
			return '>';
			break;
		case '>':
			return '<';
			break;
			
	}
	return 0;
}


int main( int argc, char *argv[] ){
	if( argc == 2 ) {
		FILE *fp=fopen(argv[1], "r");
		char ch = '\0';
		int lineCount = countLines(fp);
		rewind(fp);
		unsigned long completionScores[lineCount];
		memset(completionScores, '0', sizeof(unsigned long) * lineCount);
		int compCount = 0;
		while ( !feof(fp) ){
			unsigned int lineStart = ftell(fp);
			ch = getc(fp);
			if ( EOF == ch ) break;
			fseek(fp, lineStart, SEEK_SET);
			unsigned int length = lineLength(fp);
			fseek(fp, lineStart, SEEK_SET);
			char line[length+1];
			memset(line, '\0', sizeof(char) * (length + 1));
			char depthArr[(length+1)/2];
			memset(line, 'a', sizeof(char) * (length + 1));
			unsigned int depth=0;
			memset(line, '\0', sizeof(char) * ( ( length + 1 ) / 2 ));
			bool corrupt=false;
			while (1){
				ch = getc(fp);
				// Cant break out of switch and loop at the same time
				if ( ch == '\n' ) break;
				switch (ch) {
					case '[':
					case '(':
					case '{':
					case '<':
						depthArr[depth] = ch;
						depth++;
						break;
					case ']':
					case ')':
					case '}':
					case '>':
						depth--;
						if ( depthArr[depth] != reverse(ch) ){
							corruptLine( reverse(depthArr[ depth ]), ch, fp );
							corrupt = true;
						}
						break;
						
				}

			}
			if ( !corrupt ){
				unsigned long score=0;
				for ( int i = depth-1; i >= 0; i-- ){
					score *= 5;
					score += getScore(reverse(depthArr[i]));
				}
				completionScores[compCount++] = score;
			}
		}
		qsort(completionScores, compCount, sizeof(unsigned long), cmp_asc_unsigned_long);
		for ( int i = 0; i < compCount; i++ ){
			printf("Score %i: %lu\n", i, completionScores[i]);
		}

		printf("Middle score: %lu\n", completionScores[(  compCount / 2 )]);
		fclose(fp);
		return 0;
	} else {
		printf("You need to provide a file\n");
		return 1;
	}
}