feat: add solutions to lc problem: No.1721

No.1721.Swapping Nodes in a Linked List

Author: yanglbme

solution/1700-1799/1721.Swapping Nodes in a Linked List/README.md

@@ -154,4 +154,69 @@ public:
 };
 ```
 
+### **Go**
+
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func swapNodes(head *ListNode, k int) *ListNode {
+	fast := head
+	for k > 1 {
+		fast = fast.Next
+		k--
+	}
+	p := fast
+	slow := head
+	for fast.Next != nil {
+		slow, fast = slow.Next, fast.Next
+	}
+	q := slow
+	p.Val, q.Val = q.Val, p.Val
+	return head
+}
+```
+
+### **TypeScript**
+
+```ts
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     val: number
+ *     next: ListNode | null
+ *     constructor(val?: number, next?: ListNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.next = (next===undefined ? null : next)
+ *     }
+ * }
+ */
+
+function swapNodes(head: ListNode | null, k: number): ListNode | null {
+    let fast = head;
+    while (--k) {
+        fast = fast.next;
+    }
+    let p = fast;
+    let slow = head;
+    while (fast.next) {
+        slow = slow.next;
+        fast = fast.next;
+    }
+    let q = slow;
+    [p.val, q.val] = [q.val, p.val];
+    return head;
+}
+```
+
+### **...**
+
+```
+
+```
+
 <!-- tabs:end -->

solution/1700-1799/1721.Swapping Nodes in a Linked List/README_EN.md

@@ -123,4 +123,69 @@ public:
 };
 ```
 
+### **Go**
+
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func swapNodes(head *ListNode, k int) *ListNode {
+	fast := head
+	for k > 1 {
+		fast = fast.Next
+		k--
+	}
+	p := fast
+	slow := head
+	for fast.Next != nil {
+		slow, fast = slow.Next, fast.Next
+	}
+	q := slow
+	p.Val, q.Val = q.Val, p.Val
+	return head
+}
+```
+
+### **TypeScript**
+
+```ts
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     val: number
+ *     next: ListNode | null
+ *     constructor(val?: number, next?: ListNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.next = (next===undefined ? null : next)
+ *     }
+ * }
+ */
+
+function swapNodes(head: ListNode | null, k: number): ListNode | null {
+    let fast = head;
+    while (--k) {
+        fast = fast.next;
+    }
+    let p = fast;
+    let slow = head;
+    while (fast.next) {
+        slow = slow.next;
+        fast = fast.next;
+    }
+    let q = slow;
+    [p.val, q.val] = [q.val, p.val];
+    return head;
+}
+```
+
+### **...**
+
+```
+
+```
+
 <!-- tabs:end -->

solution/1700-1799/1721.Swapping Nodes in a Linked List/Solution.go

@@ -0,0 +1,22 @@
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func swapNodes(head *ListNode, k int) *ListNode {
+	fast := head
+	for k > 1 {
+		fast = fast.Next
+		k--
+	}
+	p := fast
+	slow := head
+	for fast.Next != nil {
+		slow, fast = slow.Next, fast.Next
+	}
+	q := slow
+	p.Val, q.Val = q.Val, p.Val
+	return head
+}

solution/1700-1799/1721.Swapping Nodes in a Linked List/Solution.ts

@@ -0,0 +1,27 @@
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     val: number
+ *     next: ListNode | null
+ *     constructor(val?: number, next?: ListNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.next = (next===undefined ? null : next)
+ *     }
+ * }
+ */
+
+function swapNodes(head: ListNode | null, k: number): ListNode | null {
+    let fast = head;
+    while (--k) {
+        fast = fast.next;
+    }
+    let p = fast;
+    let slow = head;
+    while (fast.next) {
+        slow = slow.next;
+        fast = fast.next;
+    }
+    let q = slow;
+    [p.val, q.val] = [q.val, p.val];
+    return head;
+}