合并排序

#include<stdio.h>

voidMergeSort(intr[],intn)

{

intlow,high,len;

len=1;//先将序列每元素看成是长度为1的子序列只要子序列长度小于n

while(len<n)

{

low=0;//low开始计算，至少存在2个子序列没有合并时继续合并

while(len+low<n)

{

high=low+len*2-1;

if(high>=n)high=n-1;

if(!SegmentMerge(r,low,high,len))

return;

low=high+1;

}

len*=2;

}

}

intSegmentMerge(intr[],intlow,inthigh,intlen)

{

int*r1,*r2;

intsize1,size2;

inti,j,k;

size1=len;

size2=high-low+1-len;

r1=(int*)malloc(size1*sizeof(int));

r2=(int*)malloc(size2*sizeof(int));

if(r1==NULL||r2==NULL)

return0;

//将r[low...low+size1-1]与r[low+size1...low+size1+size2-1]复制到r1、r2

for(i=0;i<size1;i++)

{

r1[i]=r[low+i];

}

for(i=0;i<size2;i++)

{

r2[i]=r[low+size1+i];

}

i=0;

j=0;

k=low;

while(i<size1&&j<size2)

{

//合并r[low...high]

if(r1[i]<=r2[j])

r[k++]=r1[i++];

elser[k++]=r2[j++];

}

while(i<size1)r[k++]=r1[i++];

while(j<size2)r[k++]=r2[j++];

free(r1);

free(r2);

return1;

}

voidmain()

{

intr[5]={5,4,3,2,1};

inti;

printf("Beforemergingsort:");

for(i=0;i<5;i++)printf("%-3d",r[i]);

printf("\n");

MergeSort(r,5);

printf("Aftermergingsort:");

for(i=0;i<5;i++)printf("%-3d",r[i]);

printf("\n");

}