Reverse Nodes in K Group Solution

Author: joshguha

24-reverseNodesInKGroup.js

@@ -0,0 +1,62 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @param {number} k
+ * @return {ListNode}
+ */
+var reverseKGroup = function (head, k) {
+    if (head === null) {
+        return null;
+    }
+
+    reverseNextKNodes = (head) => {
+        let node = head;
+        let arr = [];
+        for (let i = 0; i < k; i++) {
+            if (node === null) {
+                return head;
+            }
+            arr.push(node);
+            node = node.next;
+        }
+        let nextHead = arr[k - 1].next;
+        for (let i = arr.length - 1; i >= 1; i--) {
+            arr[i].next = arr[i - 1];
+        }
+        arr[0].next = reverseNextKNodes(nextHead);
+        return arr[k - 1];
+    };
+
+    return reverseNextKNodes(head);
+};
+
+function ListNode(val, next) {
+    this.val = val === undefined ? 0 : val;
+    this.next = next === undefined ? null : next;
+}
+
+f = new ListNode(9);
+e = new ListNode(8, f);
+d = new ListNode(7, e);
+c = new ListNode(6, d);
+b = new ListNode(5, c);
+a = new ListNode(4, b);
+
+printLinkedList = (head) => {
+    let result = [];
+    let node = head;
+    while (node !== null) {
+        result.push(node);
+        node = node.next;
+    }
+
+    console.log(result);
+};
+
+printLinkedList(reverseKGroup(a, 4));