strictly_inc_subarray.cpp

// increasing subarrays in O(n) time.
#include<bits/stdc++.h>
using namespace std;

int countIncreasing(int arr[], int n)
{
    int cnt = 0;  // Initialize result

    // Initialize length of current increasing
    // subarray
    int len = 1;

    // Traverse through the array
    for (int i=0; i < n-1; ++i)
    {
        // If arr[i+1] is greater than arr[i],
        // then increment length
        if (arr[i + 1] > arr[i])
            len++;

        // Else Update count and reset length
        else
        {
            cnt += (((len - 1) * len) / 2);
            len = 1;
        }
    }

    // If last length is more than 1
    if (len > 1)
        cnt += (((len - 1) * len) / 2);

    return cnt;
}

// Driver program
int main()
{
  int arr[] = {1, 2, 2, 4};
  int n = sizeof(arr)/sizeof(arr[0]);
  cout << "Count of strictly increasing subarrays is "
       << countIncreasing(arr, n);
  return 0;
}