Data Structure Array: Maximum of all subarrays of size k

http://www.geeksforgeeks.org/maximum-of-all-subarrays-of-size-k/

 1 #include <iostream>
 2 #include <vector>
 3 #include <algorithm>
 4 #include <queue>
 5 #include <stack>
 6 #include <string>
 7 #include <fstream>
 8 #include <map>
 9 using namespace std;
10 
11 void printKMax(int arr[], int n, int k) {
12     deque<int> S;
13     S.push_back(0);
14     for (int i = 1; i < k; i++) {
15         while (!S.empty() && arr[i] >= arr[S.back()]) S.pop_back();
16         S.push_back(i);
17     }
18     for (int i = k; i < n; i++) {
19         cout << arr[S.front()] << " ";
20         while (!S.empty() && i - k >= S.front()) S.pop_front();
21         while (!S.empty() && arr[S.back()] <= arr[i]) S.pop_back();
22         S.push_back(i);
23     }
24     cout << arr[S.front()] << endl;
25 }
26 
27 int main() {
28     int arr[7] = {12, 1, 78, 90, 57, 89, 56};
29     printKMax(arr, 7, 3);
30     return 0;
31 }