236. 二叉树的最近公共祖先 - 力扣（LeetCode）
递归
lson、rson左右子树；
深度优先遍历，遍历到p或者q就返回ture；
class Solution {
public:TreeNode* ans;bool dfs(TreeNode* root, TreeNode* p, TreeNode* q){if(root == nullptr){return false;}bool lson = dfs(root->left, p, q);bool rson = dfs(root->right, p, q);if((lson && rson) || (root->val == p->val || root->val == q->val) && (lson || rson)){ans = root;}return lson || rson || (root->val == p->val || root->val == q->val);}TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {dfs(root, p, q);return ans;}
};
