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POInsert new node at the beginning of Linked-List
 

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    <p>In a simple Linked List implementation on C, I couldn’t figure out a line of function named insert(). It takes a char and add to the linked list in alphabetical order. The line is about creating a new node when the list is empty. And since there will be only one node on the list, the line should be like I’ve commented, am I wrong?</p> <pre><code>/****************************************************/ void insert( ListNodePtr *sPtr, char value ){ ListNodePtr newPtr; ListNodePtr previousPtr; ListNodePtr currentPtr; newPtr = malloc( sizeof( ListNode) ); if( newPtr != NULL ){ //is space available newPtr-&gt;data = value; //place value in node newPtr-&gt;nextPtr = NULL; //node does not link to another node previousPtr = NULL; currentPtr = *sPtr; //indirection to startPtr while( currentPtr != NULL &amp;&amp; value &gt; currentPtr-&gt;data ){ previousPtr = currentPtr; //walk to ... currentPtr = currentPtr-&gt;nextPtr; //... next node } //insert new node at the beginning of the list if( previousPtr == NULL ){ newPtr-&gt;nextPtr = *sPtr; /////////////////////////////////////////////// newPtr-&gt;nextPtr = NULL ??? *sPtr = newPtr; } else{ //insert new node between previousPtr and currentPtr previousPtr-&gt;nextPtr = newPtr; newPtr-&gt;nextPtr = currentPtr; } } else printf( "%c not inserted. No memory available.\n", value); }//end-of insert /*******************************************************/ </code></pre> <p>the typedef instructions in main() are;</p> <pre><code>typedef struct listNode ListNode; typedef ListNode* ListNodePtr; </code></pre> <p>and the function insert() is called in main() like this;</p> <pre><code>insert( &amp;startPtr, item); </code></pre> <p>initialization of startPointer in main();</p> <pre><code>ListNodePtr startPtr = NULL; </code></pre>
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