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    <p>Starting at the beginning, if you do not set <code>front</code> and <code>rear</code> somewhere to NULL, then none of this works right.</p> <p>Then lets look at <code>push()</code>:</p> <p>When the list is empty, you set <code>front</code> and <code>rear</code> equal to <code>temp</code>. That's good. When there is a <code>front</code> you set <code>front-&gt;next= temp ;</code> This is not good if you already added something else in the list. The idea should be to use <code>rear</code> to always point to the last thing added to the list, and always add to the end of <code>rear</code>.</p> <p>So you should do:</p> <pre><code>void push(int value) { struct Node * temp= (struct Node *) malloc( sizeof( struct Node)) ; temp-&gt; Data= value ; temp-&gt; next= NULL ; fprintf(stderr, "Calling push with %d, temp at %lx.\n", value, temp) ; if ( rear) { rear-&gt; next= temp ; rear= temp ; } else { front= rear= temp ; } fprintf(stderr, "push done: front = %lx, rear = %lx\n", (long) front, (long) rear) ; } </code></pre> <p>Similarly, you have things a bit backwards on <code>pop()</code>. You look at <code>rear</code> and also check <code>rear-&gt;next</code>. <code>rear-&gt;next</code> should <strong>always</strong> be <code>NULL</code>. Instead, just take the first thing off of <code>front</code>. Worse than that though is that you look at the value of <code>rear</code> before even checking that its empty. This is going to do bad things. So test the pointer for being valid first, then read its value:</p> <pre><code>int pop() { int retval= -1 ; if ( front ) { struct Node * temp= front ; front= front-&gt; next ; if ( ! front ) { rear= front ; } retval= temp-&gt; Data ; free( temp) ; } return retval ; } </code></pre> <p>This should get you operating. }</p>
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    1. COThis replaces the first/last every time you push.
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    2. CO@PandaBearSoup why do you think `first` is replaced every time you `push()` ?
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    3. COI've just tested it, nothing is added to the list. I really appreciate your help so far, and understand what you are getting at. Using this to display list: void display() { struct Node *var=front; if(var!=NULL) { printf("\nElements are as: "); while(var!=NULL) { printf("\t%d",var->Data); var=var->next; } printf("\n"); } else printf("\nQueue is Empty"); }
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