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Author: Stuart Reges (on 2014/02/13)

Write a method collapse that collapses a list of integers by replacing each successive pair of integers with the sum of the pair. For example, if a variable called list stores this sequence of values: 

        [7, 2, 8, 9, 4, 13, 7, 1, 9, 10]

and the following call is made: 

        list.collapse();

The first pair should be collapsed into 9 (7 + 2), the second pair should be collapsed into 17 (8 + 9), the third pair should be collapsed into 17 (4 + 13) and so on to yield: 

        [9, 17, 17, 8, 19]

If the list stores an odd number of elements, the final element is not collapsed. For example, the sequence: 

        [1, 2, 3, 4, 5]

would collapse into: 

        [3, 7, 5]

with the 5 at the end of the list unchanged.

You are writing a method for the ArrayIntList class discussed in lecture (handout 3): 

        public class ArrayIntList {
            private int[] elementData; // list of integers
            private int size;          // current # of elements in the list

            <methods>
        }

You are not to call any other ArrayIntList methods to solve this problem, you are not allowed to define any auxiliary data structures (no array, ArrayList, etc), and your solution must run in O(n) time.

Type your solution here:


This is a partial class problem. Submit code that will become part of an existing Java class as described. You do not need to write the complete class, just the portion described in the problem.

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