# LeetCode 2058. Find the Minimum and Maximum Number of Nodes Between Critical Points

https://leetcode.com/problems/find-the-minimum-and-maximum-number-of-nodes-between-critical-points/description/

## 題目大意

找 linked list 中的 critical points 並回傳任兩 critical points 的最小距離跟最大距離

critical points 少於兩點回傳 `{-1,-1}`

題目給的 linked list 保證至少包含兩個 node

## 思考

最大距離就是 critical points 的頭尾距離 (最後找到跟最先找到的位置距離)
最小則需要一直更新比大小

class Solution
{
public:
    vector<int> nodesBetweenCriticalPoints(ListNode *head)
    {
        if (!head->next->next)
            return {-1, -1};

        int minDist = INT_MAX;
        int maxFront = -1, maxBack = -1;
        int idx = 1;
        ListNode *prev = head;
        ListNode *curr = head->next;

        while (curr->next)
        {
            if (curr->val > prev->val && curr->val > curr->next->val || curr->val < prev->val && curr->val < curr->next->val)
            {
                if (maxFront == -1)
                    maxFront = idx;
                if (maxBack != -1)
                    minDist = min(minDist, idx - maxBack);
                maxBack = idx;
            }

            prev = curr;
            curr = curr->next;
            ++idx;
        }

        return minDist != INT_MAX ? vector<int>{minDist, maxBack - maxFront} : vector<int>{-1, -1};
    }
};

`if (curr->val > prev->val && curr->val > curr->next->val || curr->val < prev->val && curr->val < curr->next->val)` 的部分是判斷是否為 critical points

其實如果有看懂題目的話，這題應該挺好寫的