114.二叉树展开为链表

二叉树展开为链表

给你二叉树的根结点 root，请你将它展开为一个单链表（按前序遍历顺序）。

解析

var flatten = function (root) {
  let curr = root;
  while (curr) {
    if (curr.left) {
      let prev = curr.left;
      while (prev.right) prev = prev.right;
      prev.right = curr.right;
      curr.right = curr.left;
      curr.left = null;
    }
    curr = curr.right;
  }
};