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Wednesday 11 July 2012

Reverse a linked list recursively


void RecursiveReverse(struct node** headRef) {
struct node* first;
struct node* rest;
if (*headRef == NULL) return; // empty list base case
first = *headRef; // suppose first = {1, 2, 3}
rest = first->next; // rest = {2, 3}
if (rest == NULL) return; // empty rest base case
RecursiveReverse(&rest); // Recursively reverse the smaller {2, 3} case
// after: rest = {3, 2}
first->next->next = first; // put the first elem on the end of the list
first->next = NULL; // (tricky step -- make a drawing)
*headRef = rest; // fix the head pointer
}

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