Create and print a tree in C - c

Question

I am trying to create a program that creates a tree from all the words in a file and the same words sorted.
Here is the code I have:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define SIZE 30
typedef struct node *tree;
typedef struct node {
tree left;
tree right;
struct dictionary {
char *word;
char *sortedWord;
} value;
} node;
void swap(char *a,char *b){
char tmp;
tmp = *a;
*a = *b;
*b = tmp;
}
char * bubble_sort(char *word){
char *ptr = word;
int n = strlen(word);
int i,j;
for(i=0;i<n-1;i++)
for(j=0;j<n-i-1;j++)
if(*(ptr+j)>*(ptr+j+1))
swap((ptr+j),(ptr+j+1));
return word;
}
char *RemoveNewLines(char *word){
char *newString = malloc(SIZE * sizeof(char));
char ch;
int currentLetter = 0;
int len = strlen(word);
while (currentLetter < len){
ch = word[currentLetter];
if (ch != '\n'){
newString[currentLetter] = ch;
}
else {
newString[currentLetter] = '\0';
}
currentLetter++;
}
return newString;
}
void createTree(tree memory){
// FILE *fp = fopen("words.txt","r");
// FILE *fp = fopen("words_no_duplicates1.txt","r");
FILE *fp = fopen("words_no_duplicates2.txt","r");
char *word = (char *)malloc(SIZE * sizeof(char));
if(fp == NULL)
{
perror("Error opening file");
exit(1);
}
// create the top node of the tree
node seedNode;
memory = &seedNode;
// initially just store the seed in the tree
memory->left = NULL;
memory->right = NULL;
fgets (word,SIZE,fp);
memory->value.word = (char *)malloc(SIZE * sizeof(char));
memory->value.word = strcpy(memory->value.word,RemoveNewLines(word));
// printf("%s\n",memory->value.word);
memory->value.sortedWord = (char *)malloc(SIZE * sizeof(char));
memory->value.sortedWord = strcpy(memory->value.sortedWord,bubble_sort(RemoveNewLines(word)));
// printf("%s\n",memory->value.sortedWord);
// printf("\n");
while ( fgets (word,SIZE,fp) != NULL){
memory->left = NULL;
memory->right = NULL;
memory->value.word = (char *)malloc(SIZE * sizeof(char));
memory->value.word = strcpy(memory->value.word,RemoveNewLines(word));
memory->value.sortedWord = (char *)malloc(SIZE * sizeof(char));
memory->value.sortedWord = strcpy(memory->value.sortedWord,bubble_sort(RemoveNewLines(word)));
// printf("%s\t %s\n",memory->value.word,memory->value.sortedWord);
// printf("%s\n",memory->value.word);
// printf("%s\n",memory->value.sortedWord);
// printf("\n");
}
fclose(fp);
}
void printTree(tree memory){
if (memory != NULL){
printTree(memory->left);
printf("%s",memory->value.word);
printf("%s",memory->value.sortedWord);
printf("\n");
printTree(memory->right);
}
}
int main(){
node seedNode;
tree memory = &seedNode;
createTree(memory);
printTree(memory);
return 0;
}
If I uncomment the print statements in createTree function, it all looks ok and prints what I want. But if I try to use printTree function then it ends with "Segmentation fault".
Where do I go wrong?
You can test with random file which contains one word per line.
#
After Joachim Pileborg reply, I changed my code as follows:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define SIZE 30
typedef struct node *tree;
typedef struct node {
tree left;
tree right;
struct dictionary {
char *word;
char *sortedWord;
} value;
} node;
node seedNode;
tree memory = &seedNode;
void swap(char *a,char *b){
char tmp;
tmp = *a;
*a = *b;
*b = tmp;
}
char * bubble_sort(char *word){
char *ptr = word;
int n = strlen(word);
int i,j;
for(i=0;i<n-1;i++)
for(j=0;j<n-i-1;j++)
if(*(ptr+j)>*(ptr+j+1))
swap((ptr+j),(ptr+j+1));
return word;
}
char *RemoveNewLines(char *word){
char *newString = malloc(SIZE * sizeof(char));
char ch;
int currentLetter = 0;
int len = strlen(word);
while (currentLetter < len){
ch = word[currentLetter];
if (ch != '\n'){
newString[currentLetter] = ch;
}
else {
newString[currentLetter] = '\0';
}
currentLetter++;
}
return newString;
}
tree * createTree(tree *memory){
// FILE *fp = fopen("words.txt","r");
FILE *fp = fopen("words_no_duplicates1.txt","r");
char *word = (char *)malloc(SIZE * sizeof(char));
if(fp == NULL)
{
perror("Error opening file");
exit(1);
}
// create the top node of the tree
//node seedNode;
// initially just store the seed in the tree
(*memory)->left = NULL;
(*memory)->right = NULL;
fgets (word,SIZE,fp);
(*memory)->value.word = (char *)malloc(SIZE * sizeof(char));
(*memory)->value.word = strcpy((*memory)->value.word,RemoveNewLines(word));
// printf("%s\n",memory->value.word);
(*memory)->value.sortedWord = (char *)malloc(SIZE * sizeof(char));
(*memory)->value.sortedWord = strcpy((*memory)->value.sortedWord,bubble_sort(RemoveNewLines(word)));
// printf("%s\n",memory->value.sortedWord);
// printf("\n");
while ( fgets (word,SIZE,fp) != NULL){
(*memory)->left = NULL;
(*memory)->right = NULL;
(*memory)->value.word = (char *)malloc(SIZE * sizeof(char));
(*memory)->value.word = strcpy((*memory)->value.word,RemoveNewLines(word));
(*memory)->value.sortedWord = (char *)malloc(SIZE * sizeof(char));
(*memory)->value.sortedWord = strcpy((*memory)->value.sortedWord,bubble_sort(RemoveNewLines(word)));
// printf("%s\t %s\n",memory->value.word,memory->value.sortedWord);
// printf("%s\n",memory->value.word);
// printf("%s\n",memory->value.sortedWord);
// printf("\n");
}
fclose(fp);
return memory;
}
void printTree(tree memory){
if (memory != NULL){
printTree(memory->left);
printf("%s\n",memory->value.word);
printf("%s\n",memory->value.sortedWord);
printf("\n");
printTree(memory->right);
}
}
int main(){
createTree(&memory);
printTree(memory);
return 0;
}
Although now createTree function looks strange to me, after executing the code I have printed the last word, and it sorted, from file words_no_duplicates1.txt (these are the values memory->value.word, and memory->value.sortedWord) The trees memory->left and memory->right remains empty.
Can you please help?

Answer 1

There are many problems with your code, I will point out a couple that stood out to me.
In the createTree function you have these two lines
node seedNode;
memory = &seedNode;
Those are troublesome because first the argument memory is passed by value meaning the value passed when calling the function is copied and all you have inside the function is your local variable with its copy of the value. Changing the variable will not change the original variable you used when calling the function. You can solve this by either returning the pointer or by emulating passing by reference.
The second problem with this assignment is that you make it point to a local variable. Local variables go out of scope once the function returns, and will not exist any more. Keeping and then dereferencing a pointer to this (non-existent) variable will lead to undefined behavior, and most likely crashes. This can be solved either by not doing the assignment at all, and just rely on the pointer you pass a argument, or by dynamically allocating memory for the node.