I NEED HELP EXPLAINING EACH LINE OF THE CODE AS WELL AS EXPLAINING EACH WILDCARD
ID: 3711391 • Letter: I
Question
I NEED HELP EXPLAINING EACH LINE OF THE CODE AS WELL AS EXPLAINING EACH WILDCARD. FOR EXAMPLE : '?' OR '.......'
#include <stdio.h>
#include <stdlib.h>
#define MAXSIZE 4096
/**
* You can use this recommended helper function
* Returns true if partial_line matches pattern, starting from
* the first char of partial_line.
*/
//----------------------------------------------------------------------------------
int matches_leading(char *partial_line, char *pattern) {
int i = 0;
while(pattern[i] != '') {
if(partial_line[i] == '' || partial_line[i] == ' '){
return 0;}
if(pattern[i] == '\') {
if(partial_line[i] != pattern[i+1]) {
return 0;}
if(pattern[i+2] == '+') {
char prev_char = pattern[i+1];
int inc = 0;
while(partial_line[i+1] == prev_char) {
partial_line++;
inc = 1; }
if(pattern[i+3] == prev_char && inc)
partial_line--;
pattern = pattern + 3;
} else {
pattern++;
i++; }
} else if(pattern[i+1] == '+') {
char prev_char = pattern[i];
if(prev_char == '.'){
while(partial_line[i] != '' && partial_line[i] != pattern[i+2]) {
partial_line++; }
pattern = pattern+2;
} else {
int inc = 0;
while(partial_line[i] == prev_char) {
partial_line++;
inc = 1; }
if(pattern[i+2] == prev_char && inc)
partial_line--;
pattern = pattern + 2;
if(!inc)
return 0; }
} else if(pattern[i] == '.'){
i++;
} else if(pattern[i] == '?') {
pattern++;
} else if(partial_line[i] != pattern[i]) {
return 0;
} else {
i++; }
}
return 1;
}
//----------------------------------------------------------------------------------
char *check(char *pattern) {
char *pattern2 = (char *)malloc(MAXSIZE*sizeof(char));
int number = 0;
for(int i = 0; pattern[i] != ''; i++) {
if(pattern[i] == '\' && pattern[i+1] == '?') {
pattern2[number] = pattern[i];
number++;
i++;
pattern2[number] = pattern[i];
number++;
} else if(pattern[i+1] != '?' && pattern[i] != '?') {
pattern2[number] = pattern[i];
number++;
}
} return pattern2;
}
//----------------------------------------------------------------------------------
/**
* You may assume that all strings are properly null terminated
* and will not overrun the buffer set by MAXSIZE
*
* Implementation of the rgrep matcher function
*/
int rgrep_matches(char *line, char *pattern) {
int amount = 0;
int number = 0;
char *partial_line = (char*)malloc(MAXSIZE*sizeof(char));
while(line[amount] != '') {
amount++; }
for(int i = 0; i < amount; i++) {
for(int j = 0; j < amount; j++) {
*(partial_line+j) = line[i+j];
}
if(matches_leading(partial_line, pattern) || matches_leading(partial_line, check(pattern))){
return 1;
}
free(partial_line);
partial_line = (char*)malloc(MAXSIZE*sizeof(char));
number++;
}
return 0;
}
//-----------------------------------------------------------------
int main(int argc, char **argv) {
if (argc != 2) {
fprintf(stderr, "Usage: %s ", argv[0]);
return 2;
}
//-----------------------------------------------------------------
/* we're not going to worry about long lines */
char buf[MAXSIZE];
while (!feof(stdin) && !ferror(stdin)) {
if (!fgets(buf, sizeof(buf), stdin)) {
break;
}
if (rgrep_matches(buf, argv[1])) {
fputs(buf, stdout);
fflush(stdout);
}
}
if (ferror(stdin)) {
perror(argv[0]);
return 1;
}
return 0;
}
//-------------------------------------------------------------------
Explanation / Answer
It matches the string which is using manual regular expression for finding matched string for given criteria
Example: the string is Hello World, our expression is H?lo It can matches string which Hallo, hollo, etc... It can matches any of characters for given regular expression...
If you have any doubts, please give me comment...
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