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Given a binary search tree, write a function kthSmallest
to find the kth
smallest element in it.
Note:
You may assume k is always valid, 1 ≤ k ≤ BST‘s total elements.
/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: int kthSmallest(TreeNode* root, int k) { stack<TreeNode*> nodeStack; TreeNode* tmp=root; int kthMin = 0; int kthValue; while ((!nodeStack.empty() || tmp!=NULL) && kthMin!=k) { while (tmp != NULL) { nodeStack.push(tmp); tmp = tmp->left; } tmp = nodeStack.top(); nodeStack.pop(); kthMin++;//对中序遍历稍加修改 kthValue = tmp->val; tmp = tmp->right; } return kthValue; } };
int kthSmallest(TreeNode* root, int k) { if (!root) return 0; if (k==0) return root->val; int n=count_size(root->left); if (k==n+1) return root->val; if (n>=k){ return kthSmallest(root->left, k); } if (n<k){ return kthSmallest(root->right, k-n-1); } } int count_size(TreeNode* root){ if (!root) return 0; return 1+count_size(root->left)+count_size(root->right); }
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leetCode(46):Kth Smallest Element in a BST
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原文地址:http://blog.csdn.net/walker19900515/article/details/47002985