分治法之合并排序（C实现）

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#include <stdio.h> void merge(int a[],int p,int q,int r){    int n1=q-p+1,n2=r-q;    int b1[n1];    int b2[n2];    int i=0,j=0,temp1=p,temp2=q;    while(p<=q)    {        b1[i]=a[p];        ++i;        ++p;    }    while(q+1<=r)    {        b2[j]=a[q+1];        ++j;        ++q;    }     p=temp1;q=temp2;    i=0,j=0;    while(p<=r)    {        if(i==n1)                 {            a[p]=b2[j];            ++j;        }        else if(j==n2)        {            a[p]=b1[i];            ++i;        }             else if(b1[i]<b2[j])        {            a[p]=b1[i];            ++i;        }        else        {            a[p]=b2[j];            ++j;        }        ++p;    }} void merge_sort(int a[],int p,int r){    int q=0;    if(p<r)    {        q=(p+r)/2;        merge_sort(a,p,q);         merge_sort(a,q+1,r);        merge(a,p,q,r);    }} int main(){    int i, a[100];    srand(time(0));    for ( i = 1; i < 101; ++i ){        a[i-1] = rand() % 1001;        printf( "%3d ", a[i-1] );        if(i%15==0) printf("\n");     }    printf("\n\n");    SelectionSort(a, 100);    for ( i = 1; i < 101; ++i ){        printf( "%3d ", a[i-1] );        if(i%15==0) printf("\n");     }    getch();    return 0;}

运行效果图

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