75.二叉树两个结点的最低共同父结点

struct TreeNode {
int m_nvalue;
TreeNode* m_pLeft;
TreeNode* m_pRight;
};

TreeNode *comparent(TreeNode *root, TreeNode *first, TreeNode *second) {
if (root == 0) return 0;
if (root == first || root == second) return root;
TreeNode *left = comparent(root->m_pLeft, first, second);
TreeNode *right = comparent(root->m_pRight, first, second);
if (left == 0) return right;
if (right == 0) return left;
return root;
}