# Python | Number of elements to be removed such that product of adjacent elements is always even

Given an array of N integers. The task is to eliminate the number of elements such that in the resulting array the product of any two adjacent values is even.

Examples:

```Input  : arr[] = {1, 2, 3}
Output : 0

Input  : arr[] = {1, 3, 5, 4, 2}
Output : 2
Remove 1 and 3.```

Approach: The product of 2 numbers is even if any one of them is even. This means for every pair of consecutive numbers if both are odd then eliminate one of them.
So, to make the product of the adjacent elements even, either all elements should be even or alternative even-odd elements. So the following greedy algorithm works:

• Go through all the elements in order.
• If all elements are even then “0” is returned.
• If all elements are odd then “n” is returned.
• Otherwise, count the number of consecutive odd pair.
• Return the minimum count.

Below is the Python implementation –

 `# Python 3 implementation of the   ` `# above approach  ` `   `  `# Function to find minimum number of   ` `# eliminations such that product of all   ` `# adjacent elements is even  ` `def` `min_elimination(n, arr):  ` `    ``countOdd ``=` `0` `    ``counteven ``=` `0` `    ``# Stores the new value  ` `    ``for` `i ``in` `range``(n):  ` `           `  `        ``# Count odd and even  numbers  ` `        ``if` `(arr[i] ``%` `2``):  ` `            ``countOdd ``+``=` `1` `        ``else``: ` `            ``counteven``+``=` `1` `    ``# if all are even ` `    ``if` `counteven ``=``=` `n:  ` `        ``return` `0` ` `  `    ``# if all are odd ` `    ``if` `countOdd ``=``=` `n:  ` `        ``return` `n ` `    ``else``: ` `        ``countpair ``=` `0` `        ``for` `i ``in` `range``(``1``, n): ` `            ``if` `(arr[i] ``%` `2` `=``=` `1` `and` `arr[i``-``1``] ``%` `2` `=``=` `1``): ` `                ``countpair``+``=` `1` `        ``return` `countpair  ` `   `  `# Driver code  ` `if` `__name__ ``=``=` `'__main__'``:  ` `    ``arr ``=` `[``1``, ``2``, ``3``, ``7``, ``9``]  ` `    ``n ``=` `len``(arr)  ` `   `  `    ``print``(min_elimination(n, arr)) `

Output:

`2`

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.

My Personal Notes arrow_drop_up Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Article Tags :
Practice Tags :

Be the First to upvote.

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.