exercise1-23.c

#include <stdio.h>
#define MAXLINE 1000

int getLine(char line[], int length);
void removeComments(char in[], char out[], int len);
void clearArray(char arr[], int len);

int main(){
	char line[MAXLINE];
	char out[MAXLINE];
	int c;
	while((c=getLine(line, MAXLINE)) != EOF){
		removeComments(line, out, c);
		printf("%s", out);
		clearArray(out, MAXLINE);
	}
	return 0;
}

/* 
There are two types of comments: /* type which comment out everything inbetween
and // which comments out everything until the new line character. 

edge case: if either are used inbetween quotations. ie: printf("// /*")

possible approaches: 2 pointer method - when a quote is found, stop the slow
ptr and move fast pointer til end is found, then shift everything to the right
of the fast ptr. Maybe not the fastest, but doesn't require extra space

other approach that can be done in 1 pass: iterate thru char array, adding each
item to a second array while omitting comments. O(n) time, O(n) space.
 */

void removeComments(char in[], char out[], int len){
	int i, j = 0;
	int singleQuote = 0;
	int doubleQuote = 0;
	for(i = 0; i < len - 1; ++i){
		char cur = in[i];
		char next = in[i + 1];
		if(!singleQuote && !doubleQuote && cur  == '/' && next == '/'){
			while(in[i] != '\n' && i < len){
				++i;
			}
			out[j++] = '\n';
		}else if(!singleQuote && !doubleQuote && cur == '/' && next == '*'){
			i = i +2;
			while(i < len -1 && !(in[i] == '*' && in[i+1] == '/')){
				++i;
			}
			if(i < len - 1 && in[i] == '*' && in[i+1] == '/'){
				++i; // move over the / so we omit it
			}
		}else {
			if(singleQuote && cur == '\''){
				singleQuote = 0;
			}else if(!doubleQuote && cur == '\''){
				singleQuote = 1;
			}
			if(doubleQuote && cur == '\"'){
				doubleQuote = 0;
			}else if(!singleQuote && cur == '\"'){
				doubleQuote = 1;
			}
			out[j++] = cur;
		}
	}
	if(i == len -1){
		out[j++] = in[i];
	}
	out[j] = '\0';
}

int getLine(char line[], int len){
	int c, i;
	for(i=0; i < len-1 && (c=getchar()) != EOF && c != '\n'; ++i){
		line[i] = c;
	}
	if(c == '\n'){
		line[i] = c;
		++i;
	}
	line[i++]='\0';
	return i;
}

void clearArray(char arr[], int len){
	int i;
	for(i = 0; i < len; ++i){
		arr[i] = '\0';
	}
}