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Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.
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).”
_______3______
/ ___5__ ___1__
/ \ / 6 _2 0 8
/ 7 4
For example, the lowest common ancestor (LCA) of nodes 5 and 1 is 3. Another example is LCA of nodes 5 and 4 is 5, since a node can be a descendant of itself according to the LCA definition.
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/** * 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: TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) { if (NULL == root) { return NULL; } if (root == p || root == q) { return root; } TreeNode *left = root->left ? lowestCommonAncestor(root->left, p , q) : NULL; TreeNode *right = root->right ? lowestCommonAncestor(root->right, p , q) : NULL; if (left && right) { return root; } return left ? left : right; } };
Lowest Common Ancestor of a Binary Tree
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原文地址：http://www.cnblogs.com/SpeakSoftlyLove/p/5215158.html
