Initial commit.HEADmain

1 files changed, 29 insertions, 0 deletions

diff --git a/top-interview-questions/easy/linked_list/06_linked_list_cycle.cc b/top-interview-questions/easy/linked_list/06_linked_list_cycle.cc
new file mode 100644
index 0000000..e8b4d1d
--- /dev/null
+++ b/top-interview-questions/easy/linked_list/06_linked_list_cycle.cc
@@ -0,0 +1,29 @@
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    bool hasCycle(ListNode *head) {
+        if (!head)       return false;
+        if (!head->next) return false;
+
+        const ListNode* next1 = head;
+        const ListNode* next2 = head;
+
+        do {
+            next1 = next1->next;
+            next2 = next2->next;
+            if (next2) {
+                next2 = next2->next;
+            }
+        }
+        while ((next1 != head) && next1 && next2 && (next1 != next2));
+
+        return next1 && next2 && (next1 == next2);
+    }
+};