Merge Sort String Array in Java

Hello, I am trying to implement a merge sort algorithm that sorts an array of Strings. I have seen numerous examples of merge-sorting integers but i can not understand how to this with String. Note: I have a separate class for merge sort in which i pass my list and the size of the list. i then copy my list in the array. the method call inside the main looks like this: merge.Sort(list, list.size()) ;.

Any help would be appreciated. Thank you

View Answers

April 21, 2012 at 11:44 AM

public class MergeTestStringArray {
    public static void main(String[] args) {
        String[] array = { "John", "Anthony", "Angelina", 
                "George", "Victor", "Joe", "Jackson" };

            String[] sortedArray = mergeSort(array);
            for (int i = 0; i < sortedArray.length; i++) {
            System.out.println(sortedArray[i] + " ");
            }

    }

    public static String[] mergeSort(String[] list) {
        String [] sorted = new String[list.length];
        if (list.length == 1) {
            sorted = list;
        } else {
            int mid = list.length/2;
            String[] left = null; 
            String[] right = null;
            if ((list.length % 2) == 0) {
                left = new String[list.length/2];
                right = new String[list.length/2];
            } else { 
                left = new String[list.length/2];
                right = new String[(list.length/2)+1];
            }
            int x=0;
            int y=0;
            for ( ; x < mid; x++) {
                left[x] = list[x];
            }
            for ( ; x < list.length; x++) {
                right[y++] = list[x];
            }
            left = mergeSort(left);
            right = mergeSort(right);
            sorted = mergeArray(left,right);
        }

        return sorted;
    }

    private static String[] mergeArray(String[] left, String[] right) {
        String[] merged = new String[left.length+right.length];
        int lIndex = 0;
        int rIndex = 0;
        int mIndex = 0;
        int comp = 0;
        while (lIndex < left.length || rIndex < right.length) {
            if (lIndex == left.length) {
                merged[mIndex++] = right[rIndex++];
            } else if (rIndex == right.length) {
                merged[mIndex++] = left[lIndex++];
            } else {  
                comp = left[lIndex].compareTo(right[rIndex]);
                if (comp > 0) {
                    merged[mIndex++] = right[rIndex++];
                } else if (comp < 0) {
                    merged[mIndex++] = left[lIndex++];
                } else { 
                    merged[mIndex++] = left[lIndex++];
                }
            }   
        }
        return merged;
    }


}

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