Get minimum element from stack

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;
+} 

Stack/minimumElementOfStack.cpp

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+// https://practice.geeksforgeeks.org/problems/get-minimum-element-from-stack/1/
+// Get minimum element from stack
+
+#include<bits/stdc++.h>
+using namespace std;
+class _stack{
+stack<int> s;
+int minEle;
+public :
+    int getMin();
+    int pop();
+    void push(int);
+};
+
+int main()
+{
+   int t;
+   cin>>t;
+   while(t--)
+   {
+       int q;
+       cin>>q;
+        _stack *a = new _stack();
+       while(q--){
+
+       int qt;
+       cin>>qt;
+
+       if(qt==1)
+       {
+           //push
+           int att;
+           cin>>att;
+           a->push(att);
+       }
+       else if(qt==2)
+       {
+           //pop
+           cout<<a->pop()<<" ";
+       }
+       else if(qt==3)
+       {
+           //getMin
+           cout<<a->getMin()<<" ";
+       }
+       }
+       cout<<endl;
+   }
+
+}
+
+stack<int> min_stack;
+/*returns min element from stack*/
+int _stack :: getMin()
+{
+   if(!s.empty())
+   {
+       return min_stack.top();
+   }
+   return -1;
+}
+
+/*returns poped element from stack*/
+int _stack ::pop()
+{
+   if( !s.empty())
+   {
+       int e= s.top();
+       s.pop();
+       min_stack.pop();
+       return e;
+   }
+   return -1;
+
+}
+
+/*push element x into the stack*/
+void _stack::push(int x)
+{
+   if(s.empty())
+   {
+       s.push(x);
+       min_stack.push(x);
+       return;
+   }
+if(x>= min_stack.top()) {
+    min_stack.push(min_stack.top());
+}
+else{
+    min_stack.push(x);
+}
+   s.push(x);
+}