重排链表

1.重排链表/解1.js

@@ -0,0 +1,42 @@
+/**
+ * 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 {void} Do not return anything, modify head in-place instead.
+ */
+var reorderList = function (head) {
+  const node = head
+  let lastNode = getLastNode(node)
+  let currentNode = node
+  while (!(currentNode === lastNode || currentNode.next === lastNode)) {
+    const secNode = currentNode.next
+    const lastPrevNode = getPrevNode(node, lastNode)
+    currentNode.next = lastNode
+    lastNode.next = secNode
+    currentNode = secNode
+    lastNode = lastPrevNode
+    lastNode.next = null
+  }
+  return head
+};
+
+function getLastNode(node) {
+  let lastNode = node;
+  while (lastNode.next) {
+    lastNode = lastNode.next
+  }
+  return lastNode
+}
+
+function getPrevNode(head, node) {
+  let currentNode = head;
+  while (currentNode && currentNode.next !== node) {
+    currentNode = currentNode.next
+  }
+  return currentNode
+}