添加 problem 141

Algorithms/141.Linked List Cycle/Linked List Cycle.go

@@ -0,0 +1,23 @@
+package leetcode
+
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+
+func hasCycle(head *ListNode) bool {
+	fast := head
+	slow := head
+	for slow != nil && fast != nil && fast.Next != nil {
+		fast = fast.Next.Next
+		slow = slow.Next
+		if fast == slow {
+			return true
+		}
+	}
+	return false
+}

Algorithms/141.Linked List Cycle/Linked List Cycle_test.go

@@ -0,0 +1,6 @@
+package leetcode
+
+import "testing"
+
+func Test_Problem141(t *testing.T) {
+}

Algorithms/141.Linked List Cycle/README.md

@@ -0,0 +1,16 @@
+# [141. Linked List Cycle](https://leetcode.com/problems/linked-list-cycle/description/)
+
+## 题目
+
+Given a linked list, determine if it has a cycle in it.
+
+Follow up:
+Can you solve it without using extra space?
+
+
+
+## 题目大意
+
+判断链表是否有环，不能使用额外的空间。
+
+给 2 个指针，一个指针是另外一个指针的下一个指针。快指针一次走 2 格，慢指针一次走 1 格。如果存在环，那么前一个指针一定会经过若干圈之后追上慢的指针。

README.md

@@ -79,8 +79,8 @@
 |21|[Merge Two Sorted Lists](./Algorithms/21.merge-two-sorted-lists)|41%|Easy||
 |22|[Generate Parentheses](./Algorithms/22.generate-parentheses)|48%|Medium|[❤](https://leetcode.com/list/oussv5j)|
 |23|[Merge k Sorted Lists](./Algorithms/23.merge-k-sorted-lists)|28%|Hard||
-|24|[Swap Nodes in Pairs](./Algorithms/24.swap-nodes-in-pairs)|39%|Medium|[❤](https://leetcode.com/list/oussv5j)|
-|25|[Reverse Nodes in k-Group](./Algorithms/25.reverse-nodes-in-k-group)|31%|Hard|[❤](https://leetcode.com/list/oussv5j)|
+|24|[Swap Nodes in Pairs](./Algorithms/24.Swap-Nodes-In-Pairs)|39%|Medium|[❤](https://leetcode.com/list/oussv5j)|
+|25|[Reverse Nodes in k-Group](./Algorithms/25.Reverse-Nodes-In-k-Group)|31%|Hard|[❤](https://leetcode.com/list/oussv5j)|
 |26|[Remove Duplicates from Sorted Array](./Algorithms/26.remove-duplicates-from-sorted-array)|36%|Easy|[❤](https://leetcode.com/list/oussv5j)|
 |27|[Remove Element](./Algorithms/27.remove-element)|40%|Easy||
 |28|[Implement strStr()](./Algorithms/28.implement-strstr)|28%|Easy||
@@ -192,6 +192,8 @@
 |137|[Single Number II](./Algorithms/137.single-number-ii)|42%|Medium|[❤](https://leetcode.com/list/oussv5j)|
 |139|[Word Break](./Algorithms/139.word-break)|31%|Medium|[❤](https://leetcode.com/list/oussv5j)|
 |140|[Word Break II](./Algorithms/140.word-break-ii)|24%|Hard|[❤](https://leetcode.com/list/oussv5j)|
+|141|[Linked List Cycle](./Algorithms/140.Linked-List-Cycle)|24%|Hard|[❤](https://leetcode.com/list/oussv5j)|
+|142|[Linked List Cycle II](./Algorithms/140.Linked-List-Cycle-II)|24%|Hard|[❤](https://leetcode.com/list/oussv5j)|
 |143|[Reorder List](./Algorithms/143.reorder-list)|26%|Medium|[❤](https://leetcode.com/list/oussv5j)|
 |144|[Binary Tree Preorder Traversal](./Algorithms/144.binary-tree-preorder-traversal)|46%|Medium|[❤](https://leetcode.com/list/oussv5j)|
 |145|[Binary Tree Postorder Traversal](./Algorithms/145.binary-tree-postorder-traversal)|42%|Hard||