add mountainSubarrayProblem.cpp

Arrays-algos/mountainSubarrayProblem.cpp

@@ -0,0 +1,71 @@
+// https://practice.geeksforgeeks.org/problems/mountain-subarray-problem/1
+
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution{
+  public:
+    vector<bool> processQueries(int a[], int n, vector<pair<int, int>> &queries,
+                                int q) {
+
+        vector<bool>ans;
+        int left[n], right[n];
+        left[0]=0;
+        right[n-1]=n-1;
+        int k=0;
+
+        // left[i] stores the last index on left side which is increasing 
+        // i.e. greater than its previous element
+        for(int i=1; i<n; i++)
+            {
+                if(a[i-1]<a[i])
+                    k=i;
+                left[i]=k;
+            }
+        // right[i] will store the first index on the right side which is decreasing 
+        // i.e. greater than its next element. 
+        for(int i=n-2; i>=0; i--)  
+        {
+            if(a[i+1]<a[i])
+                k=i;
+            right[i]=k;
+
+        }
+
+        for(auto x: queries)
+        {
+            int l= x.first;
+            int r= x.second;
+
+            if(left[r]<=right[l])
+                ans.push_back(true);
+            else
+                ans.push_back(false);
+        }
+    return ans;
+    }
+};
+
+int main() {
+    int tc;
+    cin >> tc;
+    while (tc--) {
+        int n, i, q;
+        cin >> n;
+        int a[n];
+        for (i = 0; i < n; i++) {
+            cin >> a[i];
+        }
+        cin >> q;
+        vector<pair<int, int>> queries(q);
+        for (i = 0; i < q; i++) {
+            cin >> queries[i].first >> queries[i].second;
+        }
+        Solution obj;
+        auto v = obj.processQueries(a, n, queries, q);
+        for (bool u : v) {
+            cout << (u ? "Yes\n" : "No\n");
+        }
+    }
+    return 0;
+}