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POI can't create doubly linked list properly in C
 

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  1. POI can't create doubly linked list properly in C
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    <p>My list head always points to tail. What's the problem?</p> <p>My <code>linked_list.h</code>:</p> <pre><code>#ifndef LINKED_LIST #define LINKED_LIST struct node { char *data; struct node *nextElement; struct node *prevElement; }; void createList(struct node **head, struct node **tail); void fill_list (char *word, struct node **head, struct node **tail); #endif </code></pre> <p><code>main.c</code>:</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include "linked_list.h" #include &lt;string.h&gt; int main() { FILE *dataFile; char *word = (char *) calloc ( 255, sizeof(char) ); /* Create empty list */ struct node *head, *tail; createList (&amp;head, &amp;tail); /*------------------------*/ /* Data file open*/ dataFile = fopen("data.txt" ,"r"); if( dataFile == NULL ) { perror("Error while opening the file.\n"); exit(EXIT_FAILURE); } /* Data reading */ while (( fscanf(dataFile, "%s", word) ) != EOF ) { int i = 0; int wordsCount = 0; for (i = 0; i &lt;= strlen(word); i++) { if ( (word[i] &gt;= 'a') &amp;&amp; (word[i] &lt;= 'z') ) wordsCount = wordsCount + 1; } if ( wordsCount == strlen(word) ) { fill_list ( word, &amp;head, &amp;tail ); } } fclose(dataFile); return 0; }; </code></pre> <p>and <code>linked_list.c</code>:</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include "linked_list.h" void createList(struct node **head, struct node **tail) { *head = NULL; *tail = NULL; } void fill_list ( char *word, struct node **head, struct node **tail ) { struct node *elem, *temp; if ( (*head) == NULL ) { // printf("HEAD = NULL\n"); elem = (struct node *) malloc ( sizeof (struct node) ); elem -&gt; data = word; elem -&gt; nextElement = NULL; elem -&gt; prevElement = NULL; (*head) = elem; *tail = elem; // printf("%s\n", (*head) -&gt; data ); } else { // printf("HEAD != NULL\n"); elem = (struct node *) malloc ( sizeof (struct node) ); elem -&gt; data = word; elem -&gt; nextElement = NULL; elem -&gt; prevElement = *tail; *tail = elem; // printf("%s\n", (*head) -&gt; data ); } } </code></pre> <p>My data file: qw erty b cc. Firstly, <code>head == NULL</code>, so <code>head -&gt; data = 'qw'</code> and it should be as head all the time, but it changes to erty, then b and cc after every loop step.</p> <p>What I'm doing wrong?</p>
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    1. PO
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    1. This table or related slice is empty.
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    1. USsyb0rg
    1. USPauliuks
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    1. This table or related slice is empty.
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      1. POI can't create doubly linked list properly in C
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    2. VO
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      1. POI can't create doubly linked list properly in C
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    3. VO
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    1. COYou aren't making sure the old last element points to the new last element when you add an element to the list.
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      1. POI can't create doubly linked list properly in C
      1. USVaughn Cato
 

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