题目：

题解：

func deleteNode(root *TreeNode, key int) *TreeNode {
    var cur, curParent *TreeNode = root, nil
    for cur != nil && cur.Val != key {
        curParent = cur
        if cur.Val > key {
            cur = cur.Left
        } else {
            cur = cur.Right
        }
    }
    if cur == nil {
        return root
    }
    if cur.Left == nil && cur.Right == nil {
        cur = nil
    } else if cur.Right == nil {
        cur = cur.Left
    } else if cur.Left == nil {
        cur = cur.Right
    } else {
        successor, successorParent := cur.Right, cur
        for successor.Left != nil {
            successorParent = successor
            successor = successor.Left
        }
        if successorParent.Val == cur.Val {
            successorParent.Right = successor.Right
        } else {
            successorParent.Left = successor.Right
        }
        successor.Right = cur.Right
        successor.Left = cur.Left
        cur = successor
    }
    if curParent == nil {
        return cur
    }
    if curParent.Left != nil && curParent.Left.Val == key {
        curParent.Left = cur
    } else {
        curParent.Right = cur
    }
    return root
}