Create f6

f6

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+	
+// A Stack based C++ program to find next 
+// greater element for all array elements. 
+#include <bits/stdc++.h> 
+using namespace std; 
+
+/* prints element and NGE pair for all 
+elements of arr[] of size n */
+void printNGE(int arr[], int n) { 
+stack < int > s; 
+
+/* push the first element to stack */
+s.push(arr[0]); 
+
+// iterate for rest of the elements 
+for (int i = 1; i < n; i++) { 
+
+	if (s.empty()) { 
+	s.push(arr[i]); 
+	continue; 
+	} 
+
+	/* if stack is not empty, then 
+	pop an element from stack. 
+	If the popped element is smaller 
+	than next, then 
+	a) print the pair 
+	b) keep popping while elements are 
+	smaller and stack is not empty */
+	while (s.empty() == false && s.top() < arr[i]) 
+	{		 
+		cout << s.top() << " --> " << arr[i] << endl; 
+		s.pop(); 
+	} 
+
+	/* push next to stack so that we can find 
+	next greater for it */
+	s.push(arr[i]); 
+} 
+
+/* After iterating over the loop, the remaining 
+elements in stack do not have the next greater 
+element, so print -1 for them */
+while (s.empty() == false) { 
+	cout << s.top() << " --> " << -1 << endl; 
+	s.pop(); 
+} 
+} 
+
+/* Driver program to test above functions */
+int main() { 
+int arr[] = {11, 13, 21, 3}; 
+int n = sizeof(arr) / sizeof(arr[0]); 
+printNGE(arr, n); 
+return 0; 
+}