Given an array arr[] of positive numbers, the task is to find the maximum sum of a subsequence with the constraint that no 2 numbers in the sequence should be adjacent in the array.

Examples:

Input: arr[] = {5, 5, 10, 100, 10, 5}
Output: 110
Explanation: Pick the subsequence {5, 100, 5}.
The sum is 110 and no two elements are adjacent. This is the highest possible sum.

Maximum sum such that no two elements are adjacent: https://www.geeksforgeeks.org/maximum-sum-such-that-no-two-elements-are-adjacent/