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Qsort() doesn't work on a struct


Qsort() doesn't work on a struct

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Qsort() doesn't work on a struct
Tag : c , By : Hadley
Date : January 12 2021, 08:33 AM

I wish this helpful for you In short: Your comparison function is wrong. Citing a qsort() manual:
return ptr_b->data[2] < ptr_a->data[2];

int myComp (const void *a, const void *b)
{
    const edge_t * ptr_a = (const edge_t *)a;
    const edge_t * ptr_b = (const edge_t *)b;
    if (ptr_a->data[2] < ptr_b->data[2]) return -1;
    if (ptr_a->data[2] > ptr_b->data[2]) return 1;
    return 0;
}

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Qsort() doesnt work on a struct , Why qsort from stdlib doesnt work with double values [C] , scanf to struct doesnt work , Retrieving struct from array of struct in C for qsort , home button doesnt work ,

scanf to struct doesnt work

Tag : c , By : Thaweesak Suksuwan
Date : March 29 2020, 07:55 AM
wish helps you I'm having this function and I need to get coordinates to a structure. These are the structures:
scanf("%d %d",pf1->location.x_l,pf1->location.y_l);

scanf("%d %d",&(pf1->location.x_l), &(pf1->location.y_l));

Why qsort from stdlib doesnt work with double values? [C]

Tag : c , By : SA.
Date : March 29 2020, 07:55 AM
should help you out You want to sort doubles but you compare them as ints... Try this comparison function:
int cmpfunc (const void * a, const void * b)
{
  if (*(double*)a > *(double*)b)
    return 1;
  else if (*(double*)a < *(double*)b)
    return -1;
  else
    return 0;  
}

Retrieving struct from array of struct in C for qsort

Tag : c , By : Jack
Date : November 14 2020, 04:51 PM
I wish did fix the issue. The problem is that your typedef defines test as a pointer type, not a plain type. Then test* becomes a double-pointer, i.e. struct test**. When you write first->data1, you are applying -> operator to a pointer to pointer to struct test, which is not a pointer to a struct.
Since test* is a double-pointer, you need to rewrite your comp to dereference it once before obtaining a member, as follows:
int comp (const void *a, const void* b){
    const test* first = (const test*)a;
    const test* second = (const test*)b;
    return (*first)->data1 - (*second)->data1;
}

qsort doesnt change my array order

Tag : c , By : UpperLuck
Date : March 29 2020, 07:55 AM
Any of those help i have an array of structures (Employee): , You need to change this:
qsort(&employeeArray, 2, sizeof(employee_t), compareEmployeesBySalary);

qsort(employeeArray, 2, sizeof(employee_t *), compareEmployeesBySalary);

int compareEmployeesBySalary(const void* a, const void* b){
        employee_t* one = *(employee_t **)a;
        employee_t* two = *(employee_t **)b;

        if (one->salary == two->salary)
            return 0;
        else if (one->salary > two->salary)
            return 1;
        else
            return -1;
}

Scanf in struct containing 'double' array doesnt work?

Tag : c , By : BinaryBoy
Date : March 29 2020, 07:55 AM
should help you out The struct members x and y arrays can hold only one element each. But you are reading 2 elements as input.
In C, array index ranges from 0 to N-1. Your code has undefined behaviour due to out of bounds access.
 struct _point2d
    {
       double x[2]
       double y[2];
    };
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