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MergeSort1.java
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MergeSort1.java
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public class MergeSort1 {
public static void main(String[] args) {
int[] arr = new int[]{1, 4, 2, 0};
System.out.print("orig: ");
print(arr);
mergeSort(arr, 0, arr.length - 1);
System.out.print("sort: ");
print(arr);
}
private static void mergeSort(int[] arr, int p, int r) {
if (p < r) {
int q = (p + r)/2;
mergeSort(arr, p, q);
mergeSort(arr, q+1, r);
merge(arr, p, q, r);
}
}
private static void merge(int[] arr, int p, int q, int r) {
int leftSize = q - p + 1;
int rightSize = r - q;
int[] left = new int[leftSize + 1];
int[] right = new int[rightSize + 1];
for (int i = 0; i < left.length - 1; i++) {
left[i] = arr[p + i];
}
for (int j = 0; j < right.length - 1; j++) {
right[j] = arr[q + j];
}
left[left.length - 1] = 10000;
right[right.length - 1] = 10000;
for (int i = 0, j = 0, k = p; k <= r; k++) {
if (left[i] <= right[j]) {
arr[k] = left[i++];
} else {
arr[k] = right[j++];
}
}
}
private static void print(int[] arr) {
System.out.print(" ");
for (int i=0; i < arr.length; i++) {
System.out.print(arr[i]);
if (i < arr.length - 1) {
System.out.print(", ");
}
}
System.out.println();
}
}