golang 解法, 执行用时: 8 ms, 内存消耗: 6.8 MB, 提交时间: 2021-07-05 11:21:19

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func getMinimumDifference(root *TreeNode) int {
    ans, pre := math.MaxInt64, -1
    var dfs func(*TreeNode)
    dfs = func(node *TreeNode) {
        if node == nil {
            return
        }
        dfs(node.Left)
        if pre != -1 && node.Val -pre < ans {
            ans = node.Val - pre
        }
        pre = node.Val
        dfs(node.Right)
    }
    dfs(root)
    return ans
}