本文共 1118 字，大约阅读时间需要 3 分钟。

/*struct TreeNode {    int val;    struct TreeNode *left;    struct TreeNode *right;    TreeNode(int x) :            val(x), left(NULL), right(NULL) {    }};*/struct MyTreeNode{    TreeNode* p;    MyTreeNode* left;    MyTreeNode* right;    int sumL;    int sumR;};class Solution {public:    MyTreeNode* presolve(TreeNode* p,int& k){        if(p == NULL) return NULL;        MyTreeNode* res = new MyTreeNode();        res->p = p;        int sum1 = 0;        int sum2 = 0;        res->left = presolve(p->left,sum1);        res->right = presolve(p->right,sum2);        res->sumL = sum1;        res->sumR = sum2;        k = sum1 + sum2 + 1;        return res;    }    TreeNode* findit(MyTreeNode* p,int k){        if(p == NULL) return NULL;        if(k > p->sumL + p->sumR + 1) return NULL;        if(k == p->sumL + 1) return p->p;        if(k <= p->sumL) return findit(p->left,k);        if(k > p->sumL + 1) return findit(p->right,k-p->sumL-1);        return NULL;    }    TreeNode* KthNode(TreeNode* pRoot, int k)    {        int sum = 0;        MyTreeNode* p = presolve(pRoot,sum);        return findit(p,k);    }    };

转载地址：http://vfwji.baihongyu.com/