使用合并排序对结构数组进行排序

记得我在上面提到的意见，你的for回路未初始化i，j或k

您的排序看起来有点复杂。

有两种方法可以进行合并：

（1）复制到临时数组并合并回原始文件（这就是您正在做的事情）

（2）从原始的左/右数组合并到temp数组，然后将结果复制回原始数组（对我来说似乎更简单）

无论如何，这是重构版本：

#include <stdio.h>

typedef struct product {
    int ident;                          /* idp of a product */
    char desc[64];                      /* string that describes a product eg.
                                            "bread" */
    int price;                          /* price of the product */
    int weight;                         /* weight of the product eg. 2kg */
    int quant;                          /* quantity of the product in stock */
    int state_prod;                     /* state of a product, if its 1 its in
                                            the system else is 0 and is not in
                                            the system */
} product;

#define AMAX    28
product a[AMAX];
product aux[AMAX];

void merge_price(product a[], int low, int mid, int high);

void
mergesort_price(product a[], int low, int high)
{
    int mid = (high + low) / 2;

    if (high <= low)
        return;
    mergesort_price(a, low, mid);
    mergesort_price(a, mid + 1, high);
    merge_price(a, low, mid, high);
}

void
merge_price(product a[], int low, int mid, int high)
{
    int right;
    int left;
    int k;
    int i;

    k = 0;
    left = low;
    right = mid + 1;

    for (;  (left <= mid) && (right <= high);  ++k) {
        if (a[left].price <= a[right].price)
            aux[k] = a[left++];
        else
            aux[k] = a[right++];
    }

    for (;  left <= mid;  ++left, ++k)
        aux[k] = a[left];

    for (;  right <= high;  ++right, ++k)
        aux[k] = a[right];

    k = low;
    i = 0;
    for (;  k <= high;  ++k, ++i)
        a[k] = aux[i];
}

void
show(void)
{
    for (int idx = 0;  idx < AMAX;  ++idx)
        printf(" %d",a[idx].price);
    printf("\n");
}

int
main(void)
{

    for (int idx = 0;  idx < AMAX;  ++idx)
        a[idx].price = AMAX - idx;
    show();

    mergesort_price(a,0,AMAX - 1);
    show();
}

更新：

好的，它工作了，谢谢，但是当我尝试这样做但是对于字符串却没有用。我只是真正地更改了if语句，就像你能解释为什么它没有请。

好的，我已经创建了一个生成随机产品描述并按排序的版本price。然后根据desc[字符串排序]求助。

我使用指向比较函数的指针来完成此操作，该指针作为附加参数传递给现有函数。这类似于libcqsort函数的最后一个参数。

可以将其扩展为“多键”排序（例如price，按[或您希望的任何成员]然后按desc[ struct]排序）。请参阅：cmpbyboth和cmpbyall。

请注意，乍看之下，编译器可能会比选择（例如）内联[简单]函数cmpbyall要快，因此，两个函数都可以生成完全相同的可执行代码。cmpbyboth-O2

无论如何，这是代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#define STRMAX      64
#define GENSTR      7

typedef struct product {
    int ident;                          /* idp of a product */
    char desc[STRMAX];                  /* string that describes a product eg.
                                            "bread" */
    int price;                          /* price of the product */
    int weight;                         /* weight of the product eg. 2kg */
    int quant;                          /* quantity of the product in stock */
    int state_prod;                     /* state of a product, if its 1 its in
                                            the system else is 0 and is not in
                                            the system */
} product;

typedef int (*cmpfnc_p)(const product *,const product *);

#define AMAX    28
product a[AMAX];
product aux[AMAX];

void merge_price(product a[], int low, int mid, int high,cmpfnc_p cmpfnc);

void
mergesort_price(product a[], int low, int high, cmpfnc_p cmpfnc)
{
    int mid = (high + low) / 2;

    if (high <= low)
        return;
    mergesort_price(a, low, mid, cmpfnc);
    mergesort_price(a, mid + 1, high, cmpfnc);
    merge_price(a, low, mid, high, cmpfnc);
}

void
merge_price(product a[], int low, int mid, int high,cmpfnc_p cmpfnc)
{
    int cmpflg;
    int right;
    int left;
    int k;
    int i;

    k = 0;
    left = low;
    right = mid + 1;

    for (;  (left <= mid) && (right <= high);  ++k) {
        cmpflg = cmpfnc(&a[left],&a[right]);
        if (cmpflg <= 0)
            aux[k] = a[left++];
        else
            aux[k] = a[right++];
    }

    for (;  left <= mid;  ++left, ++k)
        aux[k] = a[left];

    for (;  right <= high;  ++right, ++k)
        aux[k] = a[right];

    k = low;
    i = 0;
    for (;  k <= high;  ++k, ++i)
        a[k] = aux[i];
}

void
show(const char *tag)
{

    printf("\n");
    printf("%s",tag);

    for (int idx = 0;  idx < AMAX;  ++idx)
        printf(" %s=%d",a[idx].desc,a[idx].price);

    printf("\n");
}

// genstr -- get random string
void
genstr(char *desc)
{
    int len;
    int idx;
    int chr;
    int carry;

    // get random string length
    len = (rand() % GENSTR) + 1;

    // fill in random string
    for (idx = 0;  idx < len;  ++idx) {
        chr = rand() % 26;
        chr += 'a';
        *desc++ = chr;
    }

    *desc = 0;
}

// cmpbyprice -- compare by price
int
cmpbyprice(const product *left,const product *right)
{
    int cmpflg;

    cmpflg = left->price - right->price;

    return cmpflg;
}

// cmpbydesc -- compare by description
int
cmpbydesc(const product *left,const product *right)
{
    int cmpflg;

    cmpflg = strcmp(left->desc,right->desc);

    return cmpflg;
}

// cmpbyboth -- compare by price description
int
cmpbyboth(const product *left,const product *right)
{
    int cmpflg;

    do {
        cmpflg = cmpbyprice(left,right);
        if (cmpflg)
            break;

        cmpflg = cmpbydesc(left,right);
        if (cmpflg)
            break;

        // add more if you like ...
    } while (0);

    return cmpflg;
}

// cmpbyall -- compare by price description [faster version]
int
cmpbyall(const product *left,const product *right)
{
    int cmpflg;

    do {
        cmpflg = left->price - right->price;
        if (cmpflg)
            break;

        cmpflg = strcmp(left->desc,right->desc);
        if (cmpflg)
            break;

        // add more if you like ...
    } while (0);

    return cmpflg;
}

int
main(int argc,char **argv)
{
    unsigned int seed;
    product *ptr;

    --argc;
    ++argv;

    if (argc > 0)
        seed = atoi(*argv);
    else
        seed = time(NULL);
    printf("SEED: %u\n",seed);
    srand(seed);

    for (int idx = 0;  idx < AMAX;  ++idx) {
        ptr = &a[idx];
        ptr->price = AMAX - idx;
        genstr(ptr->desc);
    }
    show("INITED");

    mergesort_price(a,0,AMAX - 1,cmpbyprice);
    show("BYPRICE");

    mergesort_price(a,0,AMAX - 1,cmpbydesc);
    show("BYDESC");

    mergesort_price(a,0,AMAX - 1,cmpbyboth);
    show("BYBOTH");

    mergesort_price(a,0,AMAX - 1,cmpbyall);
    show("BYALL");
}