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MergeSorter.java
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52 lines (43 loc) · 1.15 KB
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package recursion;
import java.util.Arrays;
public class MergeSorter {
public void sort(int[] data) {
mergeSort(data, 0, data.length-1);
}
private void mergeSort(int[] data, int start, int end) {
if (start < end) {
int mid = (int) Math.floor((start+end)/2);
mergeSort(data, start, mid);
mergeSort(data, mid+1, end);
merge(data, start, mid, end);
}
}
private void merge(int[] data, int start, int mid, int end) {
int sizeOfLeft = mid-start+1;
int sizeOfRight = end - mid;
int[] left = new int[sizeOfLeft];
int[] right = new int[sizeOfRight];
for (int i = 0; i < sizeOfLeft; i++) {
left[i] = data[start + i]; // be careful here
}
for (int j = 0; j < sizeOfRight; j++) {
right[j] = data[mid + 1 + j]; // be careful
}
int i = 0, j = 0;
for (int k = start; k <= end; k++) {
if ((j >= sizeOfRight) || (i < sizeOfLeft && left[i] <= right[j])) {
data[k] = left[i];
i++;
} else {
data[k] = right[j];
j++;
}
}
}
public static void main(String[] args) {
MergeSorter sorter = new MergeSorter();
int[] data = {4,1,6,9,5};
sorter.sort(data);
System.out.println(Arrays.toString(data));
}
}