142 added

Author: aQuaYi

Algorithms/0142.linked-list-cycle-ii/1.png

@@ -0,0 +1,35 @@
+# [142. Linked List Cycle II](https://leetcode.com/problems/linked-list-cycle-ii/)
+
+Given a linked list, return the node where the cycle begins. If there is no cycle, return null.
+
+To represent a cycle in the given linked list, we use an integer pos which represents the position (0-indexed) in the linked list where tail connects to. If pos is -1, then there is no cycle in the linked list.
+
+Note: Do not modify the linked list.
+
+Example 1:
+
+```text
+Input: head = [3,2,0,-4], pos = 1
+Output: tail connects to node index 1
+Explanation: There is a cycle in the linked list, where tail connects to the second node.
+```
+
+Example 2:
+
+```text
+Input: head = [1,2], pos = 0
+Output: tail connects to node index 0
+Explanation: There is a cycle in the linked list, where tail connects to the first node.
+```
+
+Example 3:
+
+```text
+Input: head = [1], pos = -1
+Output: no cycle
+Explanation: There is no cycle in the linked list.
+```
+
+Follow up:
+
+- Can you solve it without using extra space?

Algorithms/0142.linked-list-cycle-ii/2.png

@@ -0,0 +1,11 @@
+package problem0142
+
+import "github.com/aQuaYi/LeetCode-in-Go/kit"
+
+// ListNode is pre-defined...
+type ListNode = kit.ListNode
+
+func detectCycle(head *ListNode) *ListNode {
+
+	return nil
+}

Algorithms/0142.linked-list-cycle-ii/3.png

@@ -0,0 +1,52 @@
+package problem0142
+
+import (
+	"testing"
+
+	"github.com/aQuaYi/LeetCode-in-Go/kit"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// tcs is testcase slice
+var tcs = []struct {
+	ints []int
+	pos  int
+}{
+
+	{
+		[]int{3, 2, 0, -4},
+		1,
+	},
+
+	{
+		[]int{1, 2},
+		0,
+	},
+
+	{
+		[]int{1},
+		-1,
+	},
+
+	// 可以有多个 testcase
+}
+
+func Test_detectCycle(t *testing.T) {
+	ast := assert.New(t)
+
+	for _, tc := range tcs {
+		head := kit.Ints2ListWithCycle(tc.ints, tc.pos)
+		ans := head.GetNodeWith(tc.ints[tc.pos])
+		ast.Equal(ans, detectCycle(head), "输入:%v", tc)
+	}
+}
+
+func Benchmark_detectCycle(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range tcs {
+			head := kit.Ints2ListWithCycle(tc.ints, tc.pos)
+			detectCycle(head)
+		}
+	}
+}

Algorithms/0142.linked-list-cycle-ii/README.md

@@ -1,10 +1,10 @@
 {
 	"Username": "aQuaYi",
 	"Ranking": 873,
-	"Updated": "2019-04-15T19:48:38.251156934+08:00",
+	"Updated": "2019-04-15T20:27:07.119847203+08:00",
 	"Record": {
 		"Easy": {
-			"Solved": 218,
+			"Solved": 219,
 			"Total": 238
 		},
 		"Medium": {
@@ -16,7 +16,7 @@
 			"Total": 174
 		},
 		"Total": {
-			"Solved": 755,
+			"Solved": 756,
 			"Total": 817
 		}
 	},
@@ -1719,7 +1719,7 @@
 			"TitleSlug": "linked-list-cycle",
 			"PassRate": "36%",
 			"Difficulty": "Easy",
-			"IsAccepted": false,
+			"IsAccepted": true,
 			"IsPaid": false,
 			"IsFavor": false,
 			"IsNew": false,
@@ -11389,7 +11389,7 @@
 			"ID": 947,
 			"Title": "Most Stones Removed with Same Row or Column",
 			"TitleSlug": "most-stones-removed-with-same-row-or-column",
-			"PassRate": "53%",
+			"PassRate": "54%",
 			"Difficulty": "Medium",
 			"IsAccepted": true,
 			"IsPaid": false,