Question

I have been given this below problem in school, I have solved as per my understanding and solution is as below. Can someone please help me to give a better solution for the same.

Question:

Produce a software application that creates a filtered merging of two case-insensitive sorted lists. The first input list is designated as the Source list and the other as the Prefixes list. The application will produce a merged list containing items that come from the Source and Prefixes lists using the following algorithm:

An item X is in the merged list if and only if one of the following is true:

a) X is from the Source list and there is an item Y in the Prefixes list that is a case-insensitive string prefix for X.

b) X is from the Prefixes list and there is no item in the Source list for which X is a case-insensitive string prefix.

The completed merged list should be in the same sort order as the items in the original two lists.

My Solution:

public ArrayList<String> merge(List<String> srcList, List<String> preList) {
        // If Prefixes list is empty then there cannot be a new merge list
        if (preList.isEmpty()) {
            return null;
        }
        int i = 0, j = 0;
        int sourcesListSize = srcList.size();
        int prefixesListSize = preList.size();
        ArrayList<String> mergeList = new ArrayList<String>();
        // Loop through Sources list until end of the list is reached
        //ASSUMPTION: Both SourceList and PrefixList are already sorted.
        while (i < sourcesListSize && j<prefixesListSize) {
            mergeList.add(preList.get(j).concat(srcList.get(i)));
            i++;
            j++;
        }
        // If Prefixes list still have items, then add it to mergeList
        while (j < prefixesListSize) {
            mergeList.add(preList.get(j));
            j++;
        }
        return mergeList;

    }

Input:

• Source list: {"pple","ow","enver",pic,"ull"}
• PrefixList: {"a","c","d","e","f"}

MergeList={"apple",cow","denver","epic","full"}

Is my understanding correct? Is there any best other solution?

Answer 1

Since this is homework I’ll try not to give too much away, but per the definition of prefix, here are some examples:

“a” is a prefix of “Apple”

“cow” is a prefix of “Cow”

“g” is not a prefix of “Zoo”

“col” is not a prefix of “cool”

Based on that, what will the MergeList be for the following? Hint: there will be items from both SourceList and PrefixList in the correct MergeList. Post your solution and I’ll critique it. Once you understand how this part works, you’ll have a much better idea of how to code the solution.

SourceList : {“Apple”,”Pepper”,”Denver”, “Garage”, “Zoo”}

PrefixList : {“a”,”d”,”pe”,”xylophone”,”e”}