Given a list of integers, write a function that returns the largest sum of non-adjacent numbers. Numbers can be 0 or negative. For example, [2, 4, 6, 2, 5] should return 13, since we pick 2, 6, and 5. [5, 1, 1, 5] should return 10, since we pick 5 and 5. Follow-up: Can you do this in O(N) time and constant space?

daily-coding-problem-09.java

class LargestSum {

    public static int get_sum(int[] arr, int n){
        int incl = arr[0]; // Max sum including the previous element
        int excl = 0; // Max sum excluding the previous element 
        int excl_new; 
        int i;
        for (i=0; i<n; i++){
            /* current max excluding i */ 
            excl_new = (incl>excl) ? incl:excl;

            /* current max inlcuding i */ 
            incl = excl + arr[i]; 
            excl = excl_new; 
        }
        return ((incl>excl) ? incl:excl);
    }

    public static void main(String [] args){
        int[] array = {2,4,6,2,5};
        System.out.print(get_sum(array, array.length));
    }
}

You have an error in the code, you should change the i=0 to i=1 in the for loop.
You can see the error if you check the method on [5, 1, 1, 5] array, the output should be 10 and its 11.