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  • leetcode[99]Recover Binary Search Tree

    Two elements of a binary search tree (BST) are swapped by mistake.

    Recover the tree without changing its structure.

    Note:
    A solution using O(n) space is pretty straight forward. Could you devise a constant space solution?

    confused what "{1,#,2,3}" means? > read more on how binary tree is serialized on OJ.

    /**
     * Definition for binary tree
     * struct TreeNode {
     *     int val;
     *     TreeNode *left;
     *     TreeNode *right;
     *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
     * };
     */
    class Solution {
    public:
    void inOrder(TreeNode *&pre,TreeNode *&mis1,TreeNode *&mis2, TreeNode *root)
    {
        if(root==NULL)return;
        inOrder(pre,mis1,mis2,root->left);
        if(pre!=NULL&&pre->val>root->val)
        {
            if(mis1==NULL)
            {
                mis1=pre;
                mis2=root;
            }
            else
            {
                mis2=root;
            }
        }
        pre=root;
        inOrder(pre,mis1,mis2,root->right);
    }
    void recoverTree(TreeNode *root) 
    {
        TreeNode *pre=NULL, *mis1=NULL, *mis2=NULL;
        inOrder(pre,mis1,mis2,root);
        if(mis1&&mis2)
        {
            int tmp=mis1->val;
            mis1->val=mis2->val;
            mis2->val=tmp;
        }
    }
    /*
    private:
       TreeNode *pre=NULL, *mis1=NULL, *mis2=NULL;
    public:
    void inOrder(TreeNode *root)
    {
        if(root==NULL)return;
        inOrder(root->left);
        if(pre!=NULL&&pre->val>root->val)
        {
            if(mis1==NULL)
            {
                mis1=pre;
                mis2=root;
            }
            else
            {
                mis2=root;
            }
        }
        pre=root;
        inOrder(root->right);
    }
        void recoverTree(TreeNode *root) {
            inOrder(root);
            if(mis1&&mis2)
            {
                int tmp=mis1->val;
                mis1->val=mis2->val;
                mis2->val=tmp;
            }
        }
    */
    };
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  • 原文地址:https://www.cnblogs.com/Vae1990Silence/p/4281365.html
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