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    <p>The problem is in this declaration:</p> <pre><code>struct list **pre, **aft, **head; </code></pre> <p>So, they are pointers to a pointer to a list, and then, you do things like this:</p> <pre><code>*pre = NULL; </code></pre> <p>The problem is that <code>pre</code> has not been initialized, so it holds garbage at this point. You are basically setting a random address in memory to NULL. You have two options: allocate space for them (with malloc and free afterwards), or change them to be like this:</p> <pre><code>struct list *pre, *aft, *head; </code></pre> <p>That way, they can be assigned safely. Your function would be modified like this:</p> <pre><code>void reverse(struct list **temp) { struct list *pre, *aft, *head; pre = NULL; head = *temp; if(head == NULL ) { return; } else { while(head!= NULL) { aft =head-&gt;next; head-&gt;next = pre; pre = head; head = aft; printf("%d\t",pre-&gt;node); } *temp = pre; } } </code></pre> <p>Doing that, I get the following output:</p> <pre><code>10 20 30 40 50 60 70 hello 70 60 50 40 30 20 10 </code></pre> <p>EDIT:</p> <p>I've also noticed that you are changing the value of <code>head</code> inside the functions <code>insert</code> and <code>print</code>. I recommend using a temporal variable instead to iterate the list. That also frees you from that trick you were using in <code>main</code> with <code>tmp</code>.</p> <p>Anyway, the complete code modified can be seen <a href="http://ideone.com/qNZgGi" rel="nofollow">here</a>. If yours is still giving you trouble, post an update or Ideone link with the modified code that still fails.</p>
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    1. PORun time error while reversing a link list in C
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    1. USmemo1288
    1. USmemo1288
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    1. COInterestingly, you could do away with the `if` clause altogether, just keeping the body of the else clause as the whole function. When `head == NULL`, the loop will be executed zero times, and the `*temp = pre;` will assign NULL, and the condition already showed that `head`, aka `*temp`, was NULL. It simplifies the code at the possible cost of a redundant assignment (which will be about as costly as the test required to avoid making it).
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      1. USJonathan Leffler
    2. COAfter allocating space to them I am getting 0 instead of 70
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      1. USNaman
 

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