58 lines
1.7 KiB
C++
58 lines
1.7 KiB
C++
// Source : https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/
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// Author : Hao Chen
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// Date : 2015-07-17
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/**********************************************************************************
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*
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* Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given
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* nodes in the BST.
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*
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* According to the definition of LCA on Wikipedia: “The lowest common ancestor is
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* defined between two nodes v and w as the lowest node in T that has both v and w as
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* descendants (where we allow a node to be a descendant of itself).”
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*
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* _______6______
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* / \
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* ___2__ ___8__
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* / \ / \
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* 0 _4 7 9
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* / \
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* 3 5
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*
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* For example, the lowest common ancestor (LCA) of nodes 2 and 8 is 6. Another example
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* is LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself according
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* to the LCA definition.
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*
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*
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**********************************************************************************/
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/**
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* Definition for a binary tree node.
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* struct TreeNode {
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* int val;
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* TreeNode *left;
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* TreeNode *right;
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* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
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* };
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*/
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class Solution {
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public:
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TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
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while(root) {
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if (p->val > root->val && q->val > root->val) {
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root = root->right;
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continue;
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}
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if (p->val < root->val && q->val < root->val) {
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root = root->left;
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continue;
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}
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return root;
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}
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return NULL;
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}
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};
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