c: add 0876-middle-of-the-linked-list

Author: andrewmustea

c/0876-middle-of-the-linked-list.c

@@ -0,0 +1,32 @@
+/**
+ * Given the head of a singly linked list, return the middle node of the linked
+ * list.
+ *
+ * If there are two middle nodes, return the second middle node.
+ *
+ * Constraints:
+ *
+ * The number of nodes in the list is in the range [1, 100].
+ * 1 <= Node.val <= 100
+ *
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     struct ListNode *next;
+ * };
+ *
+ * Space = O(1)
+ * Time = O(n)
+ */
+
+struct ListNode* middleNode(struct ListNode* head){
+    struct ListNode* slow = head;
+    struct ListNode* fast = head;
+
+    while (fast && fast->next) {
+        slow = slow->next;
+        fast = fast->next->next;
+    }
+
+    return slow;
+}