【剑指Offer】二叉搜索树与双向链表

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题目

输入一棵二叉搜索树，将该二叉搜索树转换成一个排序的双向链表。要求不能创建任何新的结点，只能调整树中结点指针的指向。

实现

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public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;
    }
}
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private TreeNode last = null;

public TreeNode Convert(TreeNode pRootOfTree) {
    ConvertNode(pRootOfTree);

    while (last != null && last.left != null)
        last = last.left;

    return last;
}

private void ConvertNode(TreeNode root) {
    if (root == null)
        return;

    ConvertNode(root.left);

    root.left = last;
    if (last != null)
        last.right = root;
    last = root;

    ConvertNode(root.right);
}