添加 problem 876

Algorithms/876. Middle of the Linked List/876. Middle of the Linked List.go

@@ -0,0 +1,32 @@
+package leetcode
+
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+
+func middleNode(head *ListNode) *ListNode {
+	if head == nil || head.Next == nil {
+		return head
+	}
+	p1 := head
+	p2 := head
+	for p2.Next != nil && p2.Next.Next != nil {
+		p1 = p1.Next
+		p2 = p2.Next.Next
+	}
+	length := 0
+	cur := head
+	for cur != nil {
+		length++
+		cur = cur.Next
+	}
+	if length%2 == 0 {
+		return p1.Next
+	} else {
+		return p1
+	}
+}

Algorithms/876. Middle of the Linked List/876. Middle of the Linked List_test.go

@@ -0,0 +1,56 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question876 struct {
+	para876
+	ans876
+}
+
+// para 是参数
+// one 代表第一个参数
+type para876 struct {
+	one []int
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans876 struct {
+	one int
+}
+
+func Test_Problem876(t *testing.T) {
+
+	qs := []question876{
+
+		question876{
+			para876{[]int{1, 2, 3, 4, 5}},
+			ans876{3},
+		},
+		question876{
+			para876{[]int{1, 2, 3, 4}},
+			ans876{3},
+		},
+
+		question876{
+			para876{[]int{1}},
+			ans876{1},
+		},
+
+		question876{
+			para876{[]int{}},
+			ans876{},
+		},
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 876------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans876, q.para876
+		fmt.Printf("【input】:%v       【output】:%v\n", p, L2s(middleNode(S2l(p.one))))
+	}
+	fmt.Printf("\n\n\n")
+}

Algorithms/876. Middle of the Linked List/README.md

@@ -0,0 +1,37 @@
+# [876. Middle of the Linked List](https://leetcode.com/problems/middle-of-the-linked-list/)
+
+## 题目
+
+Given a non-empty, singly linked list with head node head, return a middle node of linked list.
+
+If there are two middle nodes, return the second middle node.
+
+Example 1:
+
+```c
+Input: [1,2,3,4,5]
+Output: Node 3 from this list (Serialization: [3,4,5])
+The returned node has value 3.  (The judge's serialization of this node is [3,4,5]).
+Note that we returned a ListNode object ans, such that:
+ans.val = 3, ans.next.val = 4, ans.next.next.val = 5, and ans.next.next.next = NULL.
+```
+
+Example 2:
+
+```c
+Input: [1,2,3,4,5,6]
+Output: Node 4 from this list (Serialization: [4,5,6])
+Since the list has two middle nodes with values 3 and 4, we return the second one.
+```
+
+Note:
+
+- The number of nodes in the given list will be between 1 and 100.
+
+## 题目大意
+
+输出链表中间结点。这题在前面题目中反复出现了很多次了。
+
+如果链表长度是奇数，输出中间结点是中间结点。如果链表长度是双数，输出中间结点是中位数后面的那个结点。
+
+这道题有一个很简单的做法，用 2 个指针只遍历一次就可以找到中间节点。一个指针每次移动 2 步，另外一个指针每次移动 1 步，当快的指针走到终点的时候，慢的指针就是中间节点。