Merge Sort
// MergeSort.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <iostream>
void MergeSort(int* a, int iLen);
void MergePass(int* a, int* aa, int subLength, int iLen);
void Merge(int* a, int* aa, int start1, int end1, int start2, int end2);
void PrintArray(int a[], int iLen);
int _tmain(int argc, _TCHAR* argv[])
{
int arrayToSort[] = {20, 7, 3, 4, 25, 15, 29, 12, 4, 1};
int n = sizeof(arrayToSort)/sizeof(int);
PrintArray(arrayToSort, n);
MergeSort(arrayToSort, n);
PrintArray(arrayToSort, n);
return 0;
}
void MergeSort(int* a, int iLen)
{
if(a==NULL||iLen<=0)
return;
int i=1;
int* aa = (int*) new(int[iLen]);
while(i<iLen)
{
MergePass(a,aa,i,iLen);
i*=2;
MergePass(aa,a,i,iLen);
i*=2;
}
delete[] aa;
}
void MergePass(int* a, int* aa, int subLength, int iLen)
{
int startIndex = 0;
while(startIndex+2*subLength-1<iLen)
{
Merge(a,aa,startIndex,startIndex+subLength-1,startIndex+subLength,startIndex+subLength*2-1);
startIndex=startIndex+2*subLength;
}
if(startIndex+subLength-1<iLen)
{
Merge(a,aa,startIndex,startIndex+subLength-1,startIndex+subLength,iLen);
}
else
{
while(startIndex<iLen)
{
aa[startIndex]=a[startIndex];
startIndex++;
}
}
}
void Merge(int* a, int* aa, int start1, int end1, int start2, int end2)
{
int i1= start1;
int i2= start2;
int i3= start1;
while(i1<end1&&i2<end2)
{
if(a[i1]<a[i2])
{
aa[i3++]=a[i1++];
}
else
{
aa[i3++]=a[i2++];
}
}
while(i1<=end1)
{
aa[i3++]=a[i1++];
}
while(i2<=end2)
{
aa[i3++]=a[i2++];
}
}
void PrintArray(int a[], int iLen)
{
for(int i=0; i< iLen; i++)
{
std::cout<<a[i]<<' ';
}
std::cout<<std::endl;
}
