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Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.
According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w as descendants (where we allow a node to be a descendant of itself).”
_______6______ / ___2__ ___8__ / \ / 0 _4 7 9 / 3 5
For example, the lowest common ancestor (LCA) of nodes 2 and 8 is 6. Another example is LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself according to the LCA definition.
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迭代：
1 /** 2 * Definition for a binary tree node. 3 * struct TreeNode { 4 * int val; 5 * TreeNode *left; 6 * TreeNode *right; 7 * TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8 * }; 9 */ 10 class Solution { 11 public: 12 TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) { 13 while(true){ 14 if(root->val>p->val&&root->val>q->val){ 15 root=root->left; 16 continue; 17 } 18 if(root->val<p->val&&root->val<q->val){ 19 root=root->right; 20 continue; 21 } 22 return root; 23 } 24 } 25 };
递归：
1 class Solution { 2 public: 3 TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) { 4 if(root->val>p->val&&root->val>q->val) return lowestCommonAncestor(root->left,p,q); 5 if(root->val<p->val&&root->val<q->val) return lowestCommonAncestor(root->right,p,q); 6 return root; 7 } 8 };
还有另外1题，和这题相似：Leetcode 236. Lowest Common Ancestor of a Binary Tree
Leetcode 235. Lowest Common Ancestor of a Binary Search Tree
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原文地址：http://www.cnblogs.com/Deribs4/p/5626215.html
