迭代 递归 反转链表 反转二叉树

https://leetcode-cn.com/problems/reverse-linked-list/

反转链表  迭代 递归

https://leetcode-cn.com/problems/invert-binary-tree/

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func swap(root *TreeNode) {
	if root != nil {
		t := root.Left
		root.Left = root.Right
		root.Right = t
	}
}
func invertTree(root *TreeNode) *TreeNode {
	if root != nil {
		swap(root)
		invertTree(root.Left)
		invertTree(root.Right)
	}
	return root
}

　　https://leetcode-cn.com/problems/invert-binary-tree/solution/fan-zhuan-er-cha-shu-by-leetcode-solution/

func invertTree(root *TreeNode) *TreeNode {
    if root == nil {
        return nil
    }
    left := invertTree(root.Left)
    right := invertTree(root.Right)
    root.Left = right
    root.Right = left
    return root
}

　　

https://leetcode.cn/problems/swap-nodes-in-pairs/solution/liang-liang-jiao-huan-lian-biao-zhong-de-jie-di-91/