Create 2074-reverse-nodes-in-even-length-groups.js

Author: everthis

2074-reverse-nodes-in-even-length-groups.js

@@ -0,0 +1,41 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+const reverseEvenLengthGroups = function(head) {
+  const arr = []
+  let cur = head
+  while(cur) {
+    arr.push(cur)
+    cur = cur.next
+  }
+  let len = 1, res = []
+  for(let i = 0, n = arr.length; i < n; ) {
+    let backup = len, tmp = [], rev = len % 2 === 0
+    while(len && i < n) {
+      tmp.push(arr[i])
+      i++
+      len--
+    }
+    if((tmp.length % 2 === 0) ) {
+      tmp.reverse()
+    }
+    res.push(...tmp)
+    len = backup + 1
+  }
+  for(let i = 0; i < res.length; i++) {
+    if(i === res.length - 1) res[i].next = null
+    else {
+      res[i].next = res[i + 1]
+    }
+  }
+  
+  return res[0]
+};