class Solution {
public:
    bool isTrionic(vector<int>& nums) {
        int n = nums.size(), i = 1;
        while (i < n && nums[i - 1] < nums[i]) {
            i++;
        }
        int p = i - 1;
        while (i < n && nums[i - 1] > nums[i]) {
            i++;
        }
        int q = i - 1;
        while (i < n && nums[i - 1] < nums[i]) {
            i++;
        }
        int flag = i - 1;
        return (p != 0) && (q != p) && (flag == n - 1 && flag != q);
    }
};

// Uses single pointer, and checks for all 3 required segments one after one.a