leetcode new problems

leetcode/lc3637/trionicArray.cpp

@@ -0,0 +1,20 @@
+class Solution {
+    public : 
+        bool isTrionic(vector<int> &nums){
+            int n =nums.size();
+            if(n<3) return false;
+            int p = 0;
+            int q = n-1;
+            while(p+1 <n && nums[p] < nums[p+1]) p++;
+            while(q-1>=0 && nums[q] > nums[q-1]) q--;
+            if(p==0 || q==n-1) return false;
+            while(p+1<=q){
+                if(nums[p] > nums[p+1]) p++;
+                else return false;
+            }
+            return p==q;
+        }
+};
+
+// Uses two pointers, TC : o(n) , SC : o(1)
+// finds valid p and q if they exist, adn checks for strictly decreasing between p...q