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MergeSort.java
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MergeSort.java
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import java.util.Arrays;
class MergeSort {
public static void main(String[] args) {
// Example
int[] arr = new int[] { 5, 8, 2, 6, 4, 1 };
System.out.println("Before sort");
System.out.println(Arrays.toString(arr));
mergeSort(arr, 0, arr.length - 1);
System.out.println("After sort");
System.out.println(Arrays.toString(arr));
}
static void mergeSort(int arr[], int l, int r) {
if (l < r) {
int m = (l + r) / 2;
mergeSort(arr, l, m);
mergeSort(arr, m + 1, r);
merge(arr, l, m, r);
}
}
private static void merge(int arr[], int l, int m, int r) {
int s1 = m - l + 1;
int s2 = r - m;
int left[] = new int[s1];
int right[] = new int[s2];
for (int i = 0; i < s1; ++i)
left[i] = arr[l + i];
for (int j = 0; j < s2; ++j)
right[j] = arr[m + 1 + j];
int i = 0, j = 0;
int k = l;
while (i < s1 && j < s2) {
if (left[i] <= right[j]) {
arr[k] = left[i];
i++;
} else {
arr[k] = right[j];
j++;
}
k++;
}
while (i < s1)
arr[k++] = left[i++];
while (j < s2)
arr[k++] = right[j++];
}
}