Add solution 1461、1721

leetcode/1721.Swapping-Nodes-in-a-Linked-List/1721. Swapping Nodes in a Linked List.go

@@ -0,0 +1,36 @@
+package leetcode
+
+import (
+	"github.com/halfrost/LeetCode-Go/structures"
+)
+
+// ListNode define
+type ListNode = structures.ListNode
+
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func swapNodes(head *ListNode, k int) *ListNode {
+	count := 1
+	var a, b *ListNode
+	for node := head; node != nil; node = node.Next {
+		if count == k {
+			a = node
+		}
+		count++
+	}
+	length := count
+	count = 1
+	for node := head; node != nil; node = node.Next {
+		if count == length-k {
+			b = node
+		}
+		count++
+	}
+	a.Val, b.Val = b.Val, a.Val
+	return head
+}