✨ [19] Remove Nth Node From End of List

still very confused

Author: enkr1

19/my_solution.js

@@ -0,0 +1,43 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+class ListNode {
+  constructor(val, next) {
+    this.val = (val === undefined ? 0 : val);
+    this.next = (next === undefined ? null : next);
+  }
+}
+
+const removeNthFromEnd = (head, n) => {
+  // l = slow, r = fast
+  let dummy = new ListNode(0, head),
+    l = dummy,
+    r = head;
+
+  while (n > 0) {
+    r = r.next;
+    n--;
+  }
+
+  while (null !== r) {
+    l = l.next;
+    r = r.next;
+  }
+
+  // QUESITON: I dont understand this part
+  // Delete the node
+  l.next = l.next.next;
+
+  return dummy.next;
+}
+
+let x = new ListNode(0, new ListNode(2, new ListNode(4))),
+  y = x;
+console.log(y)
+
+x.next.next = null;
+console.log(x)

19/solution.js

@@ -0,0 +1,19 @@
+const removeNthFromEnd = (head, n) => {
+  let dummy = new ListNode(0, head),
+    l = dummy,
+    r = head;
+
+  while (n > 0) {
+    r = r.next;
+    n--;
+  }
+
+  while (null !== r) {
+    l = l.next;
+    r = r.next;
+  }
+
+  l.next = l.next.next;
+
+  return dummy.next;
+}

README.md

@@ -16,6 +16,7 @@
 - [7. Generate Parentheses](./7/)
 - [11. Container With Most Water](./11/)
 - [15. 3Sum](./15/)
+- [19. Remove Nth Node From End of List](./19/)
 - [21. Merge Two Sorted Lists](./21/)
 - [22. Generate Parentheses](./22/)
 - [23. Merge k Sorted Lists](./23/)
@@ -65,7 +66,7 @@ iex ./.../solution.ex
 
 Batch create in bash
 ```ssh
-chapter=141 && mkdir ./$chapter && touch ./$chapter/my_solution.js && touch ./$chapter/solution.js && alias x="node ./$chapter/my_solution.js"
+chapter=19 && mkdir ./$chapter && touch ./$chapter/my_solution.js && touch ./$chapter/solution.js && alias x="node ./$chapter/my_solution.js"
 ```
 > And now you can use `x` for quick debug.