寻找最近祖先

//二叉搜索树

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */
struct TreeNode* lowestCommonAncestor(struct TreeNode* root, struct TreeNode* p, struct TreeNode* q) {
    if(root == NULL) return NULL;
    if(p->val > q->val) swap(p, q);
    if(roo->val == p->val || root->val == q->val){
        return root->val == p->val ? p : q;
    }
    if(p->val < root->val && q->val > root->val) return root;
    if(root->val > q->val) return lowestCommonAncestor(root->left, p, q);
    return lowestCommonAncestor(root->right, p : q);
}


//普通二叉树


struct TreeNode* lowestCommonAncestor(struct TreeNode* root, struct TreeNode* p, struct TreeNode* q) {
    if(root == NULL) return NULL;
    if(root->val == p->val || root->val == q->val){
        return root->val == p->val ? p : q;
    }
    struct TreeNode *temp1 = lowestCommonAncestor(root->left, p, q);
    struct TreeNode *temp2 = lowestCommonAncestor(root->right, p, q);
    if(temp1 == NULL && temp2 == NULL) return NULL;
    if(temp1 == NULl || temp2 == NULL){
        return temp1 == NULL ? temp2 : temp2;
    }
    return root;
}