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leetcode (235, 236) lowest common ancestor

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Leetcode 235. Lowest Common Ancestor of a Binary Search Tree
Leetcode 236. Lowest Common Ancestor of a Binary Tree

Leetcode 235. Lowest Common Ancestor of a Binary Search Tree

Leetcode 235. Lowest Common Ancestor of a Binary Search Tree

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).”

class Solution {
public:
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
        if (root->val < p->val && root->val < q->val)
            return lowestCommonAncestor(root->right, p, q);
        if (root->val > p->val && root->val > q->val)
            return lowestCommonAncestor(root->left, p, q);
        return root;
    }
};

Leetcode 236. Lowest Common Ancestor of a Binary Tree

Leetcode 236. Lowest Common Ancestor of a Binary Tree

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.

class Solution {
public:
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
         if (!root || root==p || root == q) return root;
         TreeNode* t1 = lowestCommonAncestor(root->left, p, q);
         TreeNode* t2 = lowestCommonAncestor(root->right, p, q);
         if (t1 && t2)  return root;
         return t1 ? t1:t2;
    }
};