算法 第四版 2.2.8

由图可知，排序有序数组为线性的

package Cap2_2;

import edu.princeton.cs.introcs.StdDraw;
import edu.princeton.cs.introcs.StdOut;
import edu.princeton.cs.introcs.StdRandom;
import Cap1.Stopwatch;
import Cap2_1.Selection;
import Cap2_1.sortTemplate;

public class Merge extends sortTemplate{
	private static int cnt=0; // 访问数组的次数
	private static Comparable[] aux;
	
	public static void sort(Comparable[] a){
		aux = new Comparable[a.length];
		sort(a, 0, a.length-1);
	}
	private static void sort(Comparable[] a, int lo, int hi){ //自顶向下
		if(hi<=lo) return;
		int mid = lo + (hi-lo)/2;
		sort(a, lo, mid);
		sort(a, mid+1, hi);
		if(less(a[mid], a[mid+1])) return;  //优化2
		merge(a, lo, mid, hi);
	}
	public static void sort2(Comparable[] a){  //自下向上
		int N = a.length;
		aux = new Comparable[N];
		for(int sz=1; szmid)                a[k]=aux[j++];
			else if (j>hi)                 a[k]=aux[i++];
			else if (less(aux[i], aux[j])) a[k]=aux[i++];
			else                           a[k]=aux[j++];
			cnt++;
		}
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		StdDraw.setXscale(0, 512);
		StdDraw.setYscale(-5, 50000);
		double lastC1=0, lastC2=0;
		for(int i=1;i<=512;i++){
			int N=i;
			Integer[] a = new Integer[N];
			for(int j=0;j