Add solution and test-cases for problem 2816

Author: 0xff-dev

leetcode/2801-2900/2816.Double-a-Number-Represented-as-a-Linked-List/README.md

@@ -0,0 +1,33 @@
+# [2816.Double a Number Represented as a Linked List][title]
+
+## Description
+You are given the `head` of a **non-empty** linked list representing a non-negative integer without leading zeroes.
+
+Return the `head` of the linked list after **doubling** it.
+
+**Example 1:**  
+
+![1](./example.png)
+
+```
+Input: head = [1,8,9]
+Output: [3,7,8]
+Explanation: The figure above corresponds to the given linked list which represents the number 189. Hence, the returned linked list represents the number 189 * 2 = 378.
+```
+
+**Example 2:**  
+
+![2](./example2.png)
+
+```
+Input: head = [9,9,9]
+Output: [1,9,9,8]
+Explanation: The figure above corresponds to the given linked list which represents the number 999. Hence, the returned linked list reprersents the number 999 * 2 = 1998. 
+```
+
+## 结语
+
+如果你同我一样热爱数据结构、算法、LeetCode，可以关注我 GitHub 上的 LeetCode 题解：[awesome-golang-algorithm][me]
+
+[title]: https://leetcode.com/problems/double-a-number-represented-as-a-linked-list
+[me]: https://github.com/kylesliu/awesome-golang-algorithm

leetcode/2801-2900/2816.Double-a-Number-Represented-as-a-Linked-List/Solution.go

@@ -1,5 +1,30 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+func Solution(head *ListNode) *ListNode {
+	if head == nil {
+		return nil
+	}
+	var do func(*ListNode, *int)
+	do = func(cur *ListNode, cf *int) {
+		if cur == nil {
+			return
+		}
+		do(cur.Next, cf)
+		v := cur.Val*2 + *cf
+		*cf = v / 10
+		v %= 10
+		cur.Val = v
+	}
+	cf := 0
+	do(head, &cf)
+	if cf != 0 {
+		node := &ListNode{Val: cf, Next: head}
+		return node
+	}
+	return head
 }

leetcode/2801-2900/2816.Double-a-Number-Represented-as-a-Linked-List/Solution_test.go

@@ -10,12 +10,11 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs *ListNode
+		expect *ListNode
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", &ListNode{Val: 1, Next: &ListNode{Val: 8, Next: &ListNode{Val: 9}}}, &ListNode{Val: 3, Next: &ListNode{Val: 7, Next: &ListNode{Val: 8}}}},
+		{"TestCase2", &ListNode{Val: 9, Next: &ListNode{Val: 9, Next: &ListNode{Val: 9}}}, &ListNode{Val: 1, Next: &ListNode{Val: 9, Next: &ListNode{Val: 9, Next: &ListNode{Val: 8}}}}},
 	}
 
 	//	开始测试
@@ -30,10 +29,10 @@ func TestSolution(t *testing.T) {
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }