Create 235. Lowest Common Ancestor of a Binary Search Tree.cpp

This solution is also valid for the general binary tree

Author: ZengruiWang

235. Lowest Common Ancestor of a Binary Search Tree.cpp

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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(!root || root == p || root == q) return root;
+        TreeNode *left = lowestCommonAncestor(root->left, p, q);
+        TreeNode *right = lowestCommonAncestor(root->right, p, q);
+        if(left && right) return root;
+        return left ? left : right;
+    }
+};