归并排序

#include <stdio.h>
#include <malloc.h>
#define MaxSize 100

typedef int KeyType;        /*关键字类型*/

typedef char ElemType[10];    /*其他数据项类型*/

typedef struct 
{    
    KeyType key;               /*关键字域*/
    ElemType data;             /*其他数据域*/
} LineList;                    /*线性表元素类型*/

void Merge(LineList R[],int low,int mid,int high) 
{
    LineList *R1;
    int i=low,j=mid+1,k=0; /*k是R1的下标,i、j分别为第1、2段的下标*/
    R1=(LineList *)malloc((high-low+1)*sizeof(LineList));  /*动态分配空间*/
    while (i<=mid && j<=high)    /*在第1段和第2段均未扫描完时循环*/
        if (R[i].key<=R[j].key)  /*将第1段中的记录放入R1中*/
        {    R1[k]=R[i];
            i++;k++; 
        }
        else                           /*将第2段中的记录放入R1中*/
        {    R1[k]=R[j];
            j++;k++; 
        }
        while (i<=mid)               /*将第1段余下部分复制到R1*/
        {  
            R1[k]=R[i];
            i++;k++; 
        }
        while (j<=high)           /*将第2段余下部分复制到R1*/
        {    R1[k]=R[j];
            j++;k++;  
        }
        for (k=0,i=low;i<=high;k++,i++) /*将R1复制回R中*/
            R[i]=R1[k];
} 

void MergePass(LineList R[],int length,int n)
{
    int i;
    for (i=0;i+2*length-1<n;i=i+2*length)     /*归并length长的两相邻子表*/
        Merge(R,i,i+length-1,i+2*length-1);
    if (i+length-1<n)                    /*余下两个子表,后者长度小于length*/
        Merge(R,i,i+length-1,n-1);     /*归并这两个子表*/
}

void MergeSort(LineList R[],int n)    /*二路归并算法*/
{
    int length;
    for (length=1;length<n;length=2*length)
        MergePass(R,length,n);
}

void main()
{
    LineList R[MaxSize];
    KeyType a[]={75,87,68,92,88,61,77,96,80,72};
    int n=10,i;
    for (i=0;i<n;i++)
        R[i].key=a[i];
    printf("排序前:");
    for (i=0;i<n;i++)
        printf("%3d",R[i].key);
    printf("\n");
    MergeSort(R,n);
    printf("排序后:");
    for (i=0;i<n;i++)
        printf("%3d",R[i].key);
    printf("\n");
}