如何在 C 中按降序对结构数组进行排序

Question

These are my structures:

struct create{
    char names[30];
    int Win;
    int Lose;
    int Draw;
    int Points;
    int Average;
    int Goals;
};

So, I was searching for a method on how to sort them, by descending order. Like, according to int Win if Win is higher than other than it should be at the top.

For ex:

Name - Win - Lose - Draw ...
Joe  -  2  -   0  -  0 ...
Bill -  1  -   0  -  1 ...
Mike -  0  -   1  -  1 ...

Is it possible? Can someone help me with this.

Answer 1

Use the standard C function qsort declared in the header <stdlib.h> creating an appropriate comparison function.

Here you are.

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

struct create{
    char names[30];
    int Win;
    int Lose;
    int Draw;
    int Points;
    int Average;
    int Goals;
};

int cmp( const void *a, const void *b )
{
    const struct create *left  = a;
    const struct create *right = b;

    return ( left->Win < right->Win ) - ( right->Win < left->Win );  
}

int main(void) 
{
    struct create a[] =
    {
        { .names = "Mike", .Win = 0, .Lose = 1, .Draw = 1 },
        { .names = "Joe",  .Win = 2, .Lose = 0, .Draw = 0 },
        { .names = "Bill", .Win = 1, .Lose = 0, .Draw = 1 },
    };

    const size_t N = sizeof( a ) / sizeof( *a );

    for ( size_t i = 0; i < N; i++ )
    {
        printf( "%-4s %d %d %d\n", a[i].names, a[i].Win, a[i].Lose, a[i].Draw );
    }

    putchar( '\n' );

    qsort( a, N, sizeof( struct create ), cmp );

    for ( size_t i = 0; i < N; i++ )
    {
        printf( "%-4s %d %d %d\n", a[i].names, a[i].Win, a[i].Lose, a[i].Draw );
    }

    putchar( '\n' );

    return 0;
}

The program output is

Mike 0 1 1
Joe  2 0 0
Bill 1 0 1

Joe  2 0 0
Bill 1 0 1
Mike 0 1 1

Answer 2

Oh man... you don't specify anything in a precise way.,,. You show almost no code, no complete example, no working code. Please, read this page to get on how to post in StackOverflow. I'll assume you are using qsort() to sort the array in ascending order, with some function called comparator1() , and assume that the function is defined as:

int comparator1(void *a, void *b);

to compare structs in order to sort in ascending order. Just write this another function:

int comparator2(void *a, void *b) 
{
    return -comparator1(a, b);
}

and pass this second comparator function to the call to qsort() . You'll get the array sorted in the opposite order than before. This way, you can control the order to be ascending or descending by just selecting one function or the other. :)

Answer 3

A typical sort looks something like:

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

struct create {
        char name[30];
        int Win;
};

int
comp(const void *va, const void *vb)
{
        const struct create *a = va;
        const struct create *b = vb;
        return a->Win > b->Win ? 1 : b->Win > a->Win ? -1 : 0;
}

int
main(void)
{
        struct create ar[] = {
                { .name = "a", .Win = 5 },
                { .name = "b", .Win = 7 },
                { .name = "c", .Win = 3 },
                { .name = "d", .Win = -1 },
                { .name = "e", .Win = 5 },
                { .name = "f", .Win = 8 }
        };
        qsort(ar, sizeof ar / sizeof *ar, sizeof *ar, comp);
        for( unsigned i = 0; i < sizeof ar / sizeof *ar; i++ ) {
                printf(" %s: %d\n", ar[i].name, ar[i].Win);
        }

        return 0;
}