标签：compare new for term 3.2 rom read public use
关键代码：
private static void sort(Comparable[] input, int lo, int hi) { if(lo >= hi)//just one entry in array return; int mid = lo + (hi-lo)/2; sort(input, lo, mid); sort(input, mid+1, hi); if(!less(input[mid+1],input[mid]))//input[mid+1] >= input[mid] return; merge(input, lo, mid, hi); }
整体：
package com.qiusongde; import edu.princeton.cs.algs4.In; import edu.princeton.cs.algs4.StdOut; public class MergeSkipMerge { private static Comparable[] aux; public static void sort(Comparable[] input) { int N = input.length; aux = new Comparable[N]; sort(input, 0, N-1); } private static void sort(Comparable[] input, int lo, int hi) { if(lo >= hi)//just one entry in array return; int mid = lo + (hi-lo)/2; sort(input, lo, mid); sort(input, mid+1, hi); if(!less(input[mid+1],input[mid]))//input[mid+1] >= input[mid] return; merge(input, lo, mid, hi); } private static void merge(Comparable[] input, int lo, int mid, int hi) { //copy input[lo,hi] to aux[lo,hi] for(int i = lo; i <= hi; i++) { aux[i] = input[i]; } int i = lo; int j = mid + 1; for(int k = lo; k <= hi; k++) { if(i > mid) input[k] = aux[j++]; else if(j > hi) input[k] = aux[i++]; else if(less(aux[j], aux[i])) input[k] = aux[j++]; else input[k] = aux[i++]; } StdOut.printf("merge(input, %4d, %4d, %4d)", lo, mid, hi); show(input);//for test } private static boolean less(Comparable v, Comparable w) { return v.compareTo(w) < 0; } private static void show(Comparable[] a) { //print the array, on a single line. for(int i = 0; i < a.length; i++) { StdOut.print(a[i] + " "); } StdOut.println(); } public static boolean isSorted(Comparable[] a) { for(int i = 1; i < a.length; i++) { if(less(a[i], a[i-1])) return false; } return true; } public static void main(String[] args) { //Read strings from standard input, sort them, and print. String[] input = In.readStrings(); show(input);//for test sort(input); assert isSorted(input); show(input);//for test } }
测试结果：
M E R G E S O R T E X A M P L E merge(input, 0, 0, 1)E M R G E S O R T E X A M P L E merge(input, 2, 2, 3)E M G R E S O R T E X A M P L E merge(input, 0, 1, 3)E G M R E S O R T E X A M P L E merge(input, 4, 5, 7)E G M R E O R S T E X A M P L E merge(input, 0, 3, 7)E E G M O R R S T E X A M P L E merge(input, 8, 8, 9)E E G M O R R S E T X A M P L E merge(input, 10, 10, 11)E E G M O R R S E T A X M P L E merge(input, 8, 9, 11)E E G M O R R S A E T X M P L E merge(input, 14, 14, 15)E E G M O R R S A E T X M P E L merge(input, 12, 13, 15)E E G M O R R S A E T X E L M P merge(input, 8, 11, 15)E E G M O R R S A E E L M P T X merge(input, 0, 7, 15)A E E E E G L M M O P R R S T X A E E E E G L M M O P R R S T X
性能对比：
For 20000 random Doubles 1000 trials
Merge is 3.6s MergeFasterM is 3.3s MergeUseInsert is 3.2s MergeSkipMerge is 3.4s
算法（Algorithms）第4版 练习 2.2.11（2）
标签：compare new for term 3.2 rom read public use
原文地址：http://www.cnblogs.com/songdechiu/p/6613083.html
