golang力扣leetcode 102. 二叉树的层序遍历

package main
func main() {
}
type TreeNode struct {
  Val   int
  Left  *TreeNode
  Right *TreeNode
}
func levelOrder(root *TreeNode) [][]int {
  if root == nil {
    return nil
  }
  result := make([][]int, 0)
  queue := make([]*TreeNode, 0)
  queue = append(queue, root)
  for len(queue) > 0 {
    cnt := make([]int, 0)
    queueSize := len(queue)
    for i := 0; i < queueSize; i++ {
      //出队
      v := queue[0]
      queue = queue[1:]
      //入队
      if v.Left != nil {
        queue = append(queue, v.Left)
      }
      if v.Right != nil {
        queue = append(queue, v.Right)
      }
      cnt = append(cnt, v.Val)
    }
    result = append(result, cnt)
  }
  return result
}