Question

Given this array

int [] myArray = {5,-11,2,3,14,5,-14,2};

You are to find the maximum sum of the values in any downsequence in an unsorted array of integers. If the array is of length zero then maxSeqValue must return Integer.MIN_VALUE.

You should print the number, 19 because the downsequence with the maximum sum is 14,5.
Downsequence number is a series of non-increasing number.

These are the codes that i used but i guess that there are some cases which is still not accounted for.
Any ideas, thanks in advance.

public class MaxDownSequence{
public int maxSeqValue(int[] a){
    int sum=Integer.MIN_VALUE;
    int maxsum=Integer.MIN_VALUE;
   for (int i=1;i<a.length;i++){
        if(a[i]<a[i-1]){
            sum = a[i] + a[i-1];
            if (sum>maxsum){
                maxsum=sum;
            }
        }
        else {
            sum=a[i];
            if (sum>maxsum){
                maxsum=sum;
            }
        }
   }
   if (a.length==0){
       return Integer.MIN_VALUE;
   }
   else{
       return maxsum;

   }
}
public static void main(String args[]){
    MaxDownSequence mySeq = new MaxDownSequence();
    int [] myArray = {5,-11,2,3,14,5,-14,2};
    System.out.println(mySeq.maxSeqValue(myArray));
}

}

Answer 1

Take the input {3,2,1} the answer should be 6 your program gives 5.

Your approach is correct, every time you test a number in the array you check if its less than (actually this should be <=) previous array element.

If it is you update sum as: sum = a[i] + a[i-1]; this is incorrect. sum in your program represents the running rum of the current subsequence. You should not be overwriting it.