0876-middle-of-the-linked-list.cpp

/**
 * Definition for singly-linked list.
 * struct ListNode {
 * int val;
 * ListNode *next;
 * ListNode() : val(0), next(nullptr) {}
 * ListNode(int x) : val(x), next(nullptr) {}
 * ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
*/

classSolution {
public:
 ListNode* middleNode(ListNode* head) {
/*
 The slow and fast pointer algorithm is used to find the middle 
 of a linked list by iterating through the list with a slow 
 pointer that moves one step at a time and a fast pointer that
 moves two steps at a time. When the fast pointer reaches the 
 end of the list, the slow pointer will be at the midpoint of the list.
*/
 ListNode *slow_pointer = head, *fast_pointer = head;
while (fast_pointer != NULL && fast_pointer->next != NULL) {
 slow_pointer = slow_pointer->next;
 fast_pointer = fast_pointer->next->next;
 }
return slow_pointer;
 }
};