236. 二叉树的最近公共祖先

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 == NULL)return root;
		if (root == q || root == p)return root;
		TreeNode* left = lowestCommonAncestor(root->left, p, q);
		TreeNode* right = lowestCommonAncestor(root->right, p, q);
		if (left != NULL && right != NULL)return root;
		else if (left != NULL && right == NULL)return left;
		else if (left == NULL && right != NULL)return right;
		else {
			return NULL;
		}
	}
};

int main() {
	TreeNode* a = new TreeNode(3);
	TreeNode* b = new TreeNode(5);
	TreeNode* c = new TreeNode(1);
	TreeNode* d = new TreeNode(6);
	TreeNode* e = new TreeNode(2);
	TreeNode* f = new TreeNode(0);
	TreeNode* g = new TreeNode(8);
	TreeNode* h = new TreeNode(7);
	TreeNode* i = new TreeNode(4);
	a->left = b;
	a->right = c;
	b->left = d;
	b->right = e;
	c->left = f;
	c->right = g;
	e->left = h;
	e->right = i;
	TreeNode* p = b;
	TreeNode* q = c;
	Solution ss;
	TreeNode* root = ss.lowestCommonAncestor(a, p, q);
	cout << root->val << endl;
	return 0;
}