归并排序（比希尔还要快）

代码

public class MergeSort {

	public static void main(String[] args) {
//		int[] arr = {8,4,5,7,1,3,2,6};
//		int[] temp = new int[arr.length];
//		System.out.println("排序前：" +Arrays.toString(arr));
//		mergeSort(arr, 0, arr.length - 1, temp);
//		System.out.println("排序后：" +Arrays.toString(arr));
		int[] arr = new int[80000000];
		int[] temp = new int[arr.length];
		for (int i = 0; i < arr.length; i++) {
			//生成一个【0，8000000】的数
			arr[i] = (int)(Math.random() * 8000000);
		}
		long start = System.currentTimeMillis();
		mergeSort(arr, 0, arr.length - 1, temp);
		long end = System.currentTimeMillis();
		System.out.println("总共花费：" + (end - start));
	}
	
	public static void mergeSort(int[] arr,int left,int right,int[] temp){
		if(left < right){
			int mid = (left + right) / 2;
			mergeSort(arr, left, mid, temp);
			mergeSort(arr, mid + 1, right, temp);
			merge(arr, left, mid, right, temp);
		}
	}
	
	public static void merge(int[] arr,int left,int mid,int right,int[] temp){
		int i = left;
		int j = mid + 1;
		int t = 0;//指向temp的当前索引
		while(i <= mid && j <= right){
			if(arr[i] < arr[j]){
				temp[t] = arr[i];
				i += 1;
				t += 1;
			}else{
				temp[t] = arr[j];
				j += 1;
				t += 1;
			}
			
		}
		while(i <= mid){
			temp[t] = arr[i];
			i += 1;
			t += 1;
		}
		while(j <= right){
			temp[t] = arr[j];
			j += 1;
			t += 1;
		}
		t = 0;
		int tempLeft = left;
		while(tempLeft <= right){
			arr[tempLeft] = temp[t];
			t += 1;
			tempLeft += 1;
		}
	}
}

效率

		//8000 0000 15156ms
		//800 0000 1378ms
		//80 0000 1118ms
		//8 0000 28ms