添加 problem 19

Algorithms/19.Remove Nth Node From End of List/README.md

@@ -0,0 +1,17 @@
+# [19. Remove Nth Node From End of List](https://leetcode.com/problems/remove-nth-node-from-end-of-list/)
+
+## 题目
+
+Given a linked list, remove the n-th node from the end of list and return its head.
+
+Example:
+
+```
+Given linked list: 1->2->3->4->5, and n = 2.
+
+After removing the second node from the end, the linked list becomes 1->2->3->5.
+```
+
+## 题目大意
+
+删除链表中倒数第 n 个结点。这道题比较简单，先循环一次拿到链表的总长度，然后循环到要删除的结点的前一个结点开始删除操作。需要注意的一个特例是，有可能要删除头结点，要单独处理。

Algorithms/19.Remove Nth Node From End of List/Remove Nth Node From End of List.go

@@ -0,0 +1,45 @@
+package leetcode
+
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func removeNthFromEnd(head *ListNode, n int) *ListNode {
+	if head == nil {
+		return nil
+	}
+	if n <= 0 {
+		return head
+	}
+	current := head
+	len := 0
+	for current != nil {
+		len++
+		current = current.Next
+	}
+	if n > len {
+		return head
+	}
+	if n == len {
+		current := head
+		head = head.Next
+		current.Next = nil
+		return head
+	}
+	current = head
+	i := 0
+	for current != nil {
+		if i == len-n-1 {
+			deleteNode := current.Next
+			current.Next = current.Next.Next
+			deleteNode.Next = nil
+			break
+		}
+		i++
+		current = current.Next
+	}
+	return head
+}

Algorithms/19.Remove Nth Node From End of List/Remove Nth Node From End of List_test.go

@@ -0,0 +1,72 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question19 struct {
+	para19
+	ans19
+}
+
+// para 是参数
+// one 代表第一个参数
+type para19 struct {
+	one []int
+	n   int
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans19 struct {
+	one []int
+}
+
+func Test_Problem19(t *testing.T) {
+
+	qs := []question19{
+
+		question19{
+			para19{[]int{1, 2, 3, 4, 5}, 1},
+			ans19{[]int{1, 2, 3, 4}},
+		},
+
+		question19{
+			para19{[]int{1, 2, 3, 4, 5}, 2},
+			ans19{[]int{1, 2, 3, 5}},
+		},
+
+		question19{
+			para19{[]int{1, 2, 3, 4, 5}, 3},
+			ans19{[]int{1, 2, 4, 5}},
+		},
+		question19{
+			para19{[]int{1, 2, 3, 4, 5}, 4},
+			ans19{[]int{1, 3, 4, 5}},
+		},
+
+		question19{
+			para19{[]int{1, 2, 3, 4, 5}, 5},
+			ans19{[]int{2, 3, 4, 5}},
+		},
+
+		question19{
+			para19{[]int{1, 2, 3, 4, 5}, 0},
+			ans19{[]int{1, 2, 3, 4, 5}},
+		},
+
+		question19{
+			para19{[]int{1, 2, 3, 4, 5}, 10},
+			ans19{[]int{1, 2, 3, 4, 5}},
+		},
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 19------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans19, q.para19
+		fmt.Printf("【input】:%v       【output】:%v\n", p, L2s(removeNthFromEnd(S2l(p.one), p.n)))
+	}
+	fmt.Printf("\n\n\n")
+}

Algorithms/2.Add-Two-Number/Add Two Numbers_test.go

@@ -77,35 +77,3 @@ func Test_Problem2(t *testing.T) {
 	}
 	fmt.Printf("\n\n\n")
 }
-
-// // convert *ListNode to []int
-// func L2s(head *ListNode) []int {
-// 	res := []int{}
-
-// 	for head != nil {
-// 		res = append(res, head.Val)
-// 		head = head.Next
-// 	}
-
-// 	return res
-// }
-
-// // convert []int to *ListNode
-// func S2l(nums []int) *ListNode {
-// 	if len(nums) == 0 {
-// 		return nil
-// 	}
-
-// 	res := &ListNode{
-// 		Val: nums[0],
-// 	}
-// 	temp := res
-// 	for i := 1; i < len(nums); i++ {
-// 		temp.Next = &ListNode{
-// 			Val: nums[i],
-// 		}
-// 		temp = temp.Next
-// 	}
-
-// 	return res
-// }