添加新题目

链表/环形链表/main.go

@@ -0,0 +1,23 @@
+package main
+
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+func main() {
+
+}
+
+func hasCycle(head *ListNode) bool {
+	hash := make(map[*ListNode]struct{})
+	for head != nil {
+		if _, ok := hash[head.Next]; ok {
+			return true
+		}
+		hash[head] = struct{}{}
+		head = head.Next
+	}
+
+	return false
+}