Creating a line counter using a Binary Search Tree **Specific Issues** - c

Question

I want to create a C file which, via a binary-search-tree, reads from a text file, takes its identifiers (eg.include, stdio, hello, etc.), sorts them alphabetically, and returns what line number they appear on.
Desired terminal output:
Identifier: Hello
Counter: 2
Lines Appeared: [4, 6]
Issues:
q1.c:28:21: error: expected expression before '{' token
28 | n -> lineList = {};
When calling insert(), for the current Node, I want to add the current lineNumber to the tree->lineList[tree->counter-1].
test.txt
#include <stdio.h>
main() {
printf("Hello world!\n");
printf("Lochlann\n");
printf("Hello world!\n");
}
quetion.c
#include <stdio.h>
#include <ctype.h>
struct Node {
char * data;
int lineList[100];
int counter;
struct Word * word;
struct Node * ltree;
struct Node * rtree;
};
struct Node * head;
struct Node * newTree(char * identifier) {
struct Node * n = malloc(sizeof(struct Node));
n -> data = malloc(strlen(identifier) + 1);
n -> lineList = {};
n -> counter = 1;
strcpy(n -> data, identifier);
n -> ltree = n -> rtree = NULL;
return n;
}
struct Node * insert(struct Node * tree, char * identifier, int lineNumber) {
if (tree == NULL)
return newTree(identifier);
int cmp = strcmp(identifier, tree -> data);
if (cmp == 0) {
tree -> counter++;
tree -> lineList[tree -> counter - 1] = lineNumber;
return tree;
}
if (cmp < 0)
tree -> ltree = insert(tree -> ltree, identifier, lineNumber);
else
tree -> rtree = insert(tree -> rtree, identifier, lineNumber);
return tree;
}
void inorder(struct Node * tree) {
if (tree == NULL)
return;
inorder(tree -> ltree);
printf("Identifier: %s\nCounter: %i\nLines Appeared: ", tree -> data, tree -> counter);
for (int i = 0; i < tree -> counter; i++) {
printf("%d", tree -> lineList[i]);
//tree -> lineList[i] = lineNumber;
}
printf("\n");
inorder(tree -> rtree);
}
main() {
FILE * fp;
fp = fopen("test.txt", "r");
char buf[200];
char id[100];
int lineNumber = 1; //the tree->lineList should be [1,1,1,1,1,1]
int j;
while (fgets(buf, 100, fp)) {
int i = 0;
int len = strlen(buf);
for (j = 0, i = 0; i < len; i++) {
if (isalpha(buf[i]) || buf[i] == '_') {
while (buf[i] && (isalnum(buf[i]) || buf[i] == '_'))
id[j++] = buf[i++];
// have id
id[j] = 0;
//third argument adding line to linelist
head = insert(head, id, lineNumber);
j = 0;
}
}
}
inorder(head);
}

Answer 1

q1.c:28:21: error: expected expression before '{' token 28 | n -> lineList = {};
The problematic code is cited right there in the error message. The immediate issue is that the line is syntactically incorrect, because {} does not represent an assignable value of any type. But underneath that, you have a deeper problem: C arrays are not assignable in the first place. You can assign to array elements, but not to whole arrays.
There is a variety of functions you could use, such as memset() or memcpy(), but in this case, your best bet might be to perform the allocation of n with calloc() instead of malloc(). One of the distinctions between these is that calloc() initializes the allocated memory to all-bytes-zero.
When calling insert(), for the current Node, I want to add the current lineNumber to the tree->lineList[tree->counter-1].
Considering that C array indexes start at 0, not 1, I guess you want to do that before incrementing the node's counter. You are instead doing it after, when counter has a value one larger. Personally, though, I would start the counter for each node at 0 instead of at 1, and then do this on insertion:
tree->lineList[tree->counter++] = lineNumber;
That uses the value of the counter as of entry to the function as the index into lineList, and also increments the counter so that the next line number will go into the next position.

Answer 2

With little else on the go, here's a "mark-up" of your code. Please consider some / most / all of these comments for this program and for others.
#include <stdio.h>
#include <ctype.h>
struct Node {
char * data; // "generic" name. "token" might be better.
int lineList[100]; // limited, but okay for now
int counter;
// struct Word * word; // unused. keep things clean.
struct Node * ltree;
struct Node * rtree;
};
struct Node * head; // global variables are not recommended
struct Node * newTree(char * identifier, int lnNum ) {
// struct Node * n = malloc(sizeof(struct Node));
struct Node * n = calloc( 1, sizeof *n ); // use calloc
/* omitting test for NULL */
n -> data = malloc(strlen(identifier) + 1);
/* omitting test for NULL */
strcpy(n -> data, identifier); // do this here
// n -> lineList = {}; // unnecessary with calloc
n->lineList[ n->counter++ ] = lnNum; // missing!!!
// with calloc(), counter starts at zero
// strcpy(n -> data, identifier); // shifted to where used
// n -> ltree = n -> rtree = NULL; // unnecessary with calloc
return n;
}
struct Node * insert(struct Node * tree, char * identifier, int lineNumber) {
if (tree == NULL)
return newTree(identifier, lineNumber ); // missing param linenumber!
int cmp = strcmp(identifier, tree -> data);
if (cmp == 0) {
// tree -> counter++;
// tree -> lineList[tree -> counter - 1] = lineNumber;
/* omitting test for overrun */
tree -> lineList[ tree->counter ] = lineNumber;
tree->counter++;
return tree;
}
if (cmp < 0)
tree -> ltree = insert(tree -> ltree, identifier, lineNumber);
else
tree -> rtree = insert(tree -> rtree, identifier, lineNumber);
return tree;
}
void inorder(struct Node * tree) {
if (tree == NULL)
return;
inorder(tree -> ltree);
printf("Identifier: %s\nCounter: %i\nLines Appeared: ", tree -> data, tree -> counter);
for (int i = 0; i < tree -> counter; i++) {
printf("%d", tree -> lineList[i]);
//tree -> lineList[i] = lineNumber;
}
printf("\n");
inorder(tree -> rtree);
}
int main() { // proper declaration of 'main()'
FILE *fp = fopen("test.txt", "r"); // fewer lines
/* omitting test for success */
char buf[200];
// char id[100]; // not needed yet
int lineNumber = 0; // got zero lines so far
// int j; // willy-nilly variables
while (fgets(buf, sizeof buf, fp)) { // compiler knows dimensions
lineNumber++; // missing!
int len = strlen(buf);
for (int i = 0; i < len; /* i++ */) { // let body decide
if (isalpha(buf[i]) || buf[i] == '_') {
int j = 0; // NOW we need 'j' and..
char id[100];
while (buf[i] && (isalnum(buf[i]) || buf[i] == '_'))
id[j++] = buf[i++]; // here, 'i' is left on next character
// have id
id[j] = '\0'; // same, but conventional
//third argument adding line to linelist
head = insert(head, id, lineNumber);
// j = 0; // don't care about j anymore
}
else i++;
}
}
inorder(head);
return 0; // optional with newer compilers
}
You could even consider 'ditching' the copying of tokens from one buffer to another. Here's a slightly tighter for() loop for main():
for( int i = 0; buf[ i ]; i++ )
if (isalpha(buf[i]) || buf[i] == '_') {
int tokStart = i;
while (buf[i] && (isalnum(buf[i]) || buf[i] == '_'))
i++; // find end of token (or line)
char c = buf[i]; // remember this character
buf[i] = '\0'; // clobber it
head = insert(head, buf + tokStart, lineNumber);
buf[i--] = c; // restore character AND decrement
}