I am trying to declare an array of pointers each of which points to int arrays of different sizes. Any ideas?
6 Answers
From your description it sounds like you are looking for a pointer to a pointer.
int **aofa;
aofa = malloc(sizeof(int*) * NUM_ARRAYS);
for (int i = 0 ; i != NUM_ARRAYS ; i++) {
aofa[i] = malloc(sizeof(int) * getNumItemsInArray(i));
}
for (int i = 0 ; i != NUM_ARRAYS ; i++) {
for (int j = 0 ; j != getNumItemsInArray(i) ; j++) {
aofa[i][j] = i + j;
}
}
NUM_ARRAYS arrays may have different number of elements, as determined by the value returned by the getNumItemsInArray(i) function.
answered Apr 6, 2012 at 3:37
Sergey Kalinichenko
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Comments
int* ar[2];
int ar1[] = {1,2, 3};
int ar2[] = {5, 6, 7, 8, 9, 10};
ar[0] = ar1;
ar[1] = ar2;
cout << ar[1][2];
Comments
C version, should help clarifying the different types of declarations:
#include <stdio.h>
int main()
{
/* let's make the arrays first */
int array_A[3] = {1, 2, 3};
int array_B[3] = {4, 5, 6};
int array_C[3] = {7, 8, 9};
/* now let's declare some pointers to such arrays: */
int (*pA)[3] = &array_A;
int (*pB)[3] = &array_B;
int (*pC)[3] = &array_C; /* notice the difference: */
/* int *pA[3] would be an array of 3 pointers to int because the [] operator*/
/* has a higher precedence than *(pointer) operator. so the statement would */
/* read: array_of_3 elements of type_pointer_to_int */
/* BUT, "int (*pA)[3]" is read: pointer_A (points to) type_array_of_3_ints! */
/* so now we need a different array to hold these pointers: */
/* this is called an_ARRAY_of_3_pointers to_type_array_of_3_ints */
int (*ARRAY[3])[3] = {pA, pB, pC};
/* along with a a double pointer to type_array_of_3_ints: */
int (**PTR)[3] = ARRAY;
/* and check that PTR now points to the first element of ARRAY: */
if (*PTR == pA) printf("PTR points to the first pointer from ARRAY \n");
PTR++;
if (*PTR == pB) printf("PTR points to the second pointer from ARRAY! YAY!\n");
return 0;
}
> $ clang prog.c -Wall -Wextra -std=gnu89 "-ansi" output:
> PTR points to the first pointer from ARRAY
> PTR points to the second pointer from ARRAY! YAY!
Comments
Check out the section "Pointers to Arrays of Objects" http://www.functionx.com/cpp/Lesson24.htm It might help you.
Comments
In C++ you can declare it like shown below.new operator can work like similar to malloc in C.
int** array = new int*[n];
Comments
#include <iostream>
using namespace std;
#define arraySize 3
const int arr1[] = {48,49,50};
const int arr2[] = {64,65,66};
const int arr3[] = {67,68,69};
typedef const int (*arrayByte);
arrayByte arrayPointer[arraySize] = {
arr1,arr2,arr3
};
void printArr(const int arr[], int size){
for(uint8_t x=0;x<size;x++){
printf("value%d=%d \n",x,arr[x]);
}
}
int main()
{
printf("Print Array 0\n");
printArr(arrayPointer[0],arraySize);
printf("Print Array 1\n");
printArr(arrayPointer[1],arraySize);
printf("Print Array 2\n");
printArr(arrayPointer[2],arraySize);
return 0;
}
try this code: C++ online
int **myarray?...std::array<std::vector<int>, 5>.