654. 最大二叉树 ​

* function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {number[]} nums
 * @return {TreeNode}
 */
var constructMaximumBinaryTree = function(nums) {
  if (!nums.length) return null
  if (nums.length === 1) return new TreeNode(nums[0])

  let max = -Number.MAX_VALUE
  let maxIndex
  // 找出最大值和最大值的索引
  for (let i = 0;i < nums.length;i++) {
    if (nums[i] > max) {
      max = nums[i]
      maxIndex = i
    }
  }

  // 从最大值 切分为左右两块递归
  const node = new TreeNode(max)
  node.left = constructMaximumBinaryTree(nums.slice(0, maxIndex))
  node.right = constructMaximumBinaryTree(nums.slice(maxIndex + 1))
  return node
};

* function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {number[]} nums
 * @return {TreeNode}
 */
var constructMaximumBinaryTree = function(nums) {
  if (!nums.length) return null
  if (nums.length === 1) return new TreeNode(nums[0])

  let max = -Number.MAX_VALUE
  let maxIndex
  // 找出最大值和最大值的索引
  for (let i = 0;i < nums.length;i++) {
    if (nums[i] > max) {
      max = nums[i]
      maxIndex = i
    }
  }

  // 从最大值 切分为左右两块递归
  const node = new TreeNode(max)
  node.left = constructMaximumBinaryTree(nums.slice(0, maxIndex))
  node.right = constructMaximumBinaryTree(nums.slice(maxIndex + 1))
  return node
};