前端算法leetcode109题解有序链表转换二叉搜索树

var sortedListToBST = function(head) {
  if(head === null){
      return null
  }
  const list = []
  while(head){
      list.push(head.val)
      head = head.next
  }
  function buildTree(list){
      const len = list.length
      if(len===0){
          return null
      }
      const mid = len>>1
      const nodeVal = list[mid]
      const l = list.slice(0,mid)
      const r = list.slice(mid+1)
      return new TreeNode(nodeVal,buildTree(l),buildTree(r))
  }
  return buildTree(list)
};

var sortedListToBST = function(head) {
  if(head === null){
      return null
  }
  const list = []
  while(head){
      list.push(head.val)
      head = head.next
  }
  function buildTree(l,r){
      if(l>r){
          return null
      }
      const mid = (l+r)>>1
      const nodeVal = list[mid]
      return new TreeNode(nodeVal,buildTree(l,mid-1),buildTree(mid+1,r))
  }
  return buildTree(0,list.length-1)
};

const sortedListToBST = (head) => {
    if (head == null){
        return null
    }
    let len = 0
    let cur = head
    while (head) {
        len++
        head = head.next
    }
    function buildTree(l,r){
        if (l > r){
            return null
        }
        const mid = (l + r) >>> 1
        const leftTree = buildTree(l, mid - 1)
        const node = new TreeNode(cur.val)
        node.left = leftTree
        cur = cur.next           
        node.right = buildTree(mid + 1, r)
        return node
  }
  return buildTree(0, len - 1)
};