logo
Tags down

shadow

Properties of a pointer to a zero length array


By : Tiff
Date : August 01 2020, 11:00 PM
it should still fix some issue Per recent CWG reflector discussion as a result of editorial issue 3178, new int[0] produces what is currently called a "past-the-end" pointer value.
It follows that a cannot be null, and a + 1 is undefined by [expr.add]/4.
code :


Share : facebook icon twitter icon

Go: how to convert unsafe.Pointer into pointer to array with unknown length?


By : Adam
Date : March 29 2020, 07:55 AM
will be helpful for those in need You first convert to an array of a type with a static length that can fit your data, then slice that array to the correct length and capacity.
code :
mapSlice := (*[1 << 30]float32)(unsafe.Pointer(&mmap[0]))[:n:n]

In C, how to sort an array of pointers where each pointer points to a variable-length array of int?


By : jacobh4535
Date : March 29 2020, 07:55 AM
should help you out As noted in the comments, the main answer is 'carefully'. The question itself doesn't say anything about sorting the content of the arrays. However, that is mentioned in one of the comments. Here's code that does the job, using the standard library function qsort() — twice. I extended the list of arrays a bit, and renamed arr6 to list to separate it from the other arrN arrays (and there is probably a better name for it than list — be my guest).
I called this qs79.c:
code :
/* SO 4335-0957 */
#include <stdio.h>
#include <stdlib.h>

void sort_arr(int num, int **list);
void print_arr(int num, int **list);

int main(void)
{
    int arr1[] = { 3, 9, 6, 7 };
    int arr2[] = { 2, 5, 5 };
    int arr3[] = { 0 };
    int arr4[] = { 1, 6 };
    int arr5[] = { 4, 5, 6, 2, 1 };
    int arr6[] = { 4, 2, 7, 1, 5 };
    int arr7[] = { 4, 2, 5, 1, 6 };
    int arr8[] = { 9, 12, 19, 18, 10, 28, 27, 15, 15, 27 };
    int arr9[] = { 4, 2, 5, 1, 5 };

    int *list[] = { arr1, arr2, arr3, arr4, arr5, arr6, arr7, arr8, arr9 };
    enum { NUM_LIST = sizeof(list) / sizeof(list[0]) };

    printf("Unsorted:\n");
    print_arr(NUM_LIST, list);
    sort_arr(NUM_LIST, list);
    printf("Sorted:\n");
    print_arr(NUM_LIST, list);
    return 0;
}

static int cmpintasc(const void *v1, const void *v2)
{
    int i1 = *(int *)v1;
    int i2 = *(int *)v2;
    return (i1 > i2) - (i1 < i2);
}

#if 0
static inline int min(int x, int y) { return (x < y) ? x : y; }

static int cmpintptrasc(const void *v1, const void *v2)
{
    int *i1 = *(int **)v1;
    int *i2 = *(int **)v2;
    int max = min(i1[0], i2[0]) + 1;
    for (int i = 1; i < max; i++)
    {
        if (i1[i] != i2[i])
            return (i1[i] > i2[i]) - (i1[i] < i2[i]);
    }
    return (i1[0] > i2[0]) - (i1[0] < i2[0]);
}
#endif

static int cmpintptrasc(const void *v1, const void *v2)
{
    int *i1 = *(int **)v1;
    int *i2 = *(int **)v2;
    return (i1[0] > i2[0]) - (i1[0] < i2[0]);
}

void sort_arr(int num, int **list)
{
    /* Sort each array in turn */
    for (int k = 0; k < num; k++)
        qsort(&list[k][1], list[k][0], sizeof(list[k][0]), cmpintasc);
    /* Sort the whole list */
    qsort(list, num, sizeof(list[0]), cmpintptrasc);
}

void print_arr(int num, int **list)
{
    for (int k = 0; k < num; k++)
    {
        printf("%d: [%d]  ", k, list[k][0]);
        for (int c = 1; c < (list[k][0] + 1); c++)
            printf("%d ", list[k][c]);
        printf("\n");
    }
}
Unsorted:
0: [3]  9 6 7 
1: [2]  5 5 
2: [0]  
3: [1]  6 
4: [4]  5 6 2 1 
5: [4]  2 7 1 5 
6: [4]  2 5 1 6 
7: [9]  12 19 18 10 28 27 15 15 27 
8: [4]  2 5 1 5 
Sorted:
0: [0]  
1: [1]  6 
2: [2]  5 5 
3: [3]  6 7 9 
4: [4]  1 2 5 5 
5: [4]  1 2 5 6 
6: [4]  1 2 5 7 
7: [4]  1 2 5 6 
8: [9]  10 12 15 15 18 19 27 27 28 
Unsorted:
0: [3]  9 6 7 
1: [2]  5 5 
2: [0]  
3: [1]  6 
4: [4]  5 6 2 1 
5: [4]  2 7 1 5 
6: [4]  2 5 1 6 
7: [9]  12 19 18 10 28 27 15 15 27 
8: [4]  2 5 1 5 
Sorted:
0: [0]  
1: [4]  1 2 5 5 
2: [4]  1 2 5 6 
3: [4]  1 2 5 6 
4: [4]  1 2 5 7 
5: [2]  5 5 
6: [1]  6 
7: [3]  6 7 9 
8: [9]  10 12 15 15 18 19 27 27 28 

Need to implement a recursive mergesort code in C using array pointer, its length and a workspace array for the merge fu


By : user1570776
Date : March 29 2020, 07:55 AM
To fix this issue The merging phase in function merge_sort iterates on both halves in parallel, taking the smallest element from either side at a time:
code :
void merge_sort(int *a, int *w, int n) {
    if (n < 2) {
        return;
    } else {
        int i, j, k;
        int n1 = n / 2;
        int *b = a + n1;
        int n2 = n - n1;

        /* sort the left half */
        merge_sort(a, w, n1);
        /* sort the right half */
        merge_sort(b, w, n2);

        /* merge the halves into w */
        for (i = j = k = 0; i < n1 && j < n2;) {
            if (a[i] <= b[j]) {
                /* get smallest value from a */
                w[k++] = a[i++];
            } else {
                /* get smallest value from b */
                w[k++] = b[j++];
            }
        }
        /* copy remaining elements from a */
        while (i < n1) {
            w[k++] = a[i++];
        }
        /* copy remaining elements from b */
        while (j < n2) {
            w[k++] = b[j++];
        }
        /* copy sorted elements back to a */
        for (i = 0; i < n; i++) {
            a[i] = w[i];
        }
    } 
}
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define ARRAY_MAX 100000

int main(void) {
    int my_array[ARRAY_MAX];
    int work_space[ARRAY_MAX];
    int i, count;
    clock_t start, end;

    count = 0;
    while (count < ARRAY_MAX && scanf("%d", &my_array[count]) == 1) {
        count += 1;
    }

    start = clock();
    merge_sort(my_array, workspace, count);
    end = clock();

    for (i = 0; i < count; i++) {
        printf("%d\n", my_array[i]);
    }

    fprintf(stderr,"%d %f\n", count, (end - start) / (double)CLOCKS_PER_SEC);

    return EXIT_SUCCESS;
}

Is it possible to find the length of an array if I have only the pointer to the first array element taking into account


By : Tapas
Date : March 29 2020, 07:55 AM
To fix the issue you can do No it's not possible. This is one of the many, many reasons that you should normally use std::vector instead of arrays.
Vectors are actually easier, safer, more powerful and more intuitive than arrays. The sooner you learn how to use them the better.

Why does the length of array shows zero when we define a set of array properties using character value instead of numeri


By : dustfree
Date : March 29 2020, 07:55 AM
will be helpful for those in need As you can check in here:
code :
var array = [];

array[0] = 1;
// Length = 1
console.log(array.length);

array["five"] = 5;
// Length still = 1
console.log(array.length);

array[1] = 1;
// Length now is = 2
console.log(array.length);

array[4] = 1;
// Length now is = 5, because you are adding an element to the position 4
console.log(array.length);
console.log(array);
Related Posts Related Posts :
  • Sending argument to an .exe via SHELLEXECUTEINFO
  • Why I can't use i/10 in FOR LOOP, C++?
  • How to use PERF_SAMPLE_READ with mmap
  • Is there any way to iterate through a struct?
  • My character counting code is miscounting characters. Why?
  • Difference between std::resize(n) and std::shrink_to_fit in C++?
  • Wildcard for C++ concepts saying "accepting anything for this template argument"
  • Which of the objects of the class A would be created first in this code snippet?
  • Floating point math accuracy, c++ vs fortran
  • C++ initialize objects with packed array of integers
  • Picking a constructor to call
  • using function call in constructor gives different result c++
  • Using strcpy to copy elements of an char array to another array
  • Templated Constructor Specialization
  • Struggling to convert an integer into a linked list. Not sure what I'm doing wrong here
  • C++: Is it better to store a console output in a macro?
  • C++ - Exception in Constructor
  • AVX: matrix dot vector, but ignore diagonal
  • Pointer To Pointer passed by reference
  • Why is this operator< overload function invisible to STL algorithms?
  • What is the correct algorithm to perform double-float division?
  • In the case of using a std::unique_ptr to automatically deallocate memory upon exiting a scoped block, why not just use
  • C++: Iterating over a string vector and using the index for putenv
  • OpenCL Matrix Multiplication Using std::vector
  • template template parameter deduction: three different compilers three different behaviors
  • C++ pull a card from deck
  • File reading with and without new line
  • store strings in stable memory in c++
  • Why is static_cast used in QT's official document
  • iterator .end() from std::list returns "0xcdcdcdcdcdcdcdcd" but .begin() as expected
  • Is std::sqrt the same as sqrt in C++
  • Iterate through std::initializer_list
  • Codeblocks c++ code doesn't run in VS 19 (vector subscript out of range)
  • Why erase on std::vector promote iterator
  • how to destroy an object in C++
  • How to create Visual Studio 2015 solution from CMake
  • Using concepts for checking if a type T has a field F
  • constructor giving error: no matching function for call to
  • search top n% of a vector member C++
  • Is this reinterpret_cast problematic in principle, and/or in practice?
  • What is the following error doing? I do not see any error with the bounds
  • Two index's of an array have same memory adress
  • how do i avoid integer division in c++?
  • Setting value to enum
  • Why the output is different how ever the formula is the same?
  • Restarting from the beginning using do while loops
  • Error: invalid initialization of reference of type
  • how to avoid to use memcpy to create a string
  • Copying the vector elements into std::array
  • Is there any class pointers in Perl in order to access member variables and functions?
  • Why the static variable is not set to 1000
  • Why can't a destructor have reference qualifiers?
  • How to print binary tree in horizontal way?
  • Comparison behavior of ' <' operator
  • Constructors in C++ Language
  • Why displayed value of b , c and y is different from my trace?
  • Undefined reference to `fftw_init_threads' while installing pHash library
  • Reading remapped hdd sectors
  • why the result is 1?
  • YouCompleteMe conf file for inspecting libraries header files without reporting the library errors
  • shadow
    Privacy Policy - Terms - Contact Us © voile276.org