[LeetCode 234,235][简单]回文链表/二叉搜索树的最近公共祖先

234.回文链表
题目链接

class Solution {
public:
    bool isPalindrome(ListNode* head) {
        ListNode *h = head;
        ListNode *f = new ListNode(0);
        ListNode *s = new ListNode(0);
        f->next = s->next = h;
        while(f && f->next){
            s = s->next;
            f = f->next->next;
        }
        ListNode *pre = NULL;
        ListNode *nxt;
        while(true){
            nxt = s->next;
            s -> next = pre;
            pre = s ;
            if(nxt)s = nxt;
            else break;
        }
        while(h!=NULL){
            if(s ->val != h ->val)return false;
            s = s->next;
            h = h->next;
        }
        return true;
    }
};

234.二叉搜索树的最近公共祖先
题目链接
由于这个数据结构建的很挫，所以也用不到什么LCA的技巧

class Solution {
public:
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
        int l = min(p->val,q->val);
        int r = max(p->val,q->val);
        while(true){
            if(root->val>r)root = root->left;
            else if(root->val < l)root = root->right;
            else return root;
        }
    }
};