归并排序算法

public class MergeSort {
	
	public static int[] merge(int[] arr1, int[] arr2) {
		int[] temp = new int[arr1.length + arr2.length];

		int start1 = 0;
		int start2 = 0;
		int end1 = arr1.length - 1;
		int end2 = arr2.length - 1;

		int index = 0;

		while (start1 <= end1 && start2 <= end2) {
			if (arr1[start1] <= arr2[start2]) {
				temp[index++] = arr1[start1++];
			} else {
				temp[index++] = arr2[start2++];
			}
		}
System.out.println("start1 " + start1 + "  end1 " + end1 + " start2 " + start2 + "  end2 " + end2);
		if (start1 > end1) {
			for (int i = start2; i <= end2; i++) {
				temp[index++] = arr2[i];
			}
		} else {
			for (int i = start1; i <= end1; i++) {
				temp[index++] = arr1[i];
			}
		}
		
		return temp;
	}
	
	public static int[] sort(int[] arr) {
		if (arr.length <= 1) return arr;
		
		int[] arr1 =sort(Arrays.copyOfRange(arr, 0, arr.length / 2));
		System.out.println("arr1 : " + Arrays.toString(arr1));
		int[] arr2 = sort(Arrays.copyOfRange(arr, arr.length / 2, arr.length));
		System.out.println("arr2 : " + Arrays.toString(arr2));		
		return merge(arr1, arr2);
		
	}
	
	public static void main(String[] args) {
		int[] arr = {2, 1, 3, 32, 1, 7, 45,32,9, 4};
		int[] result = sort(arr);
		
		for (int i = 0; i < result.length; i ++) {
			System.out.print("  " + result[i]);
		}
	}
}