自底向上的归并排序-转自算法C语言实现

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package cn.ccnu.lzc;import java.util.Random;public class DownTopTwoWayMergeSort {/** * @param args *  自底向上的归并排序：归并排序主要是完成将若干个有序子序列合并成一个 *  完整的有序子序列；自底向上的排序是归并排序的一种实现方式，将一个无 *  序的N长数组切个成N个有序子序列，然后再两两合并，然后再将合并后的N/2 *  （或者N/2 + 1）个子序列继续进行两两合并，以此类推得到一个完整的有序数组。 */public static void main(String[] args) {// TODO Auto-generated method stubint maxSize=16;TArray arr=new TArray(maxSize);for(int i=0;i<maxSize;i++){int n=new Random().nextInt(100);arr.insert(n);}arr.display();arr.MergeSort();arr.display();}}class TArray{private int[] theArray;private int nElems;public TArray(int max){theArray=new int[max];nElems=0;}public void insert(int value){theArray[nElems++]=value;}public void display(){for(int i:theArray){System.out.print(i+" ");}System.out.println();}public void MergeSort(){int[] workspace=new int[nElems];recMergeSort(workspace,0,nElems-1);}private void recMergeSort(int[] workspace, int lowerBound, int upperBound) {// TODO Auto-generated method stubint i,step;for(step=1;step<upperBound;step=2*step){for(i=0;i<=upperBound-step;i+=2*step){Merge(workspace,i,i+step,min(i+2*step-1,upperBound));}}}private void Merge(int[] workspace, int lowPtr, int highPtr, int upperBound) {// TODO Auto-generated method stubint lowBound=lowPtr;int mid=highPtr-1;int j=0;int n=upperBound-lowBound+1;while(lowPtr<=mid&&highPtr<=upperBound){if(theArray[lowPtr]<=theArray[highPtr]){workspace[j++]=theArray[lowPtr++];}else{workspace[j++]=theArray[highPtr++];}}while(lowPtr<=mid){workspace[j++]=theArray[lowPtr++];}while(highPtr<=upperBound){workspace[j++]=theArray[highPtr++];}for(j=0;j<n;j++){theArray[lowBound++]=workspace[j];}}private int min(int i, int upperBound) {// TODO Auto-generated method stubreturn (i<upperBound)?i:upperBound;}}
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