Combine or merge 2 array with loop or function - c

Question

I'm new to the C world. I'm using Visual 2010. I need to create an array from 2 other arrays, or a function to merge them; I come from PHP so I'm sorry if this is stupid. I tested some loop without success..
a real example could be helpful:
int arrayA[5] = {3,2,1,4,5}
int arrayB[5] = {6,3,1,2,9}
And the printed expected output of the third arrayC should be :
arrayC {
[3][6]
[2][3]
[2][1]
[4][2]
[5][9]
}

Answer 1

A straightforward approach can look the following way
#include <stdio.h>
#define N 5
int main( void )
{
int a[N] = { 3, 2, 2, 4, 5 };
int b[N] = { 6, 3, 1, 2, 9 };
int c[N][2];
for ( size_t i = 0; i < N; i++ )
{
c[i][0] = a[i]; c[i][1] = b[i];
}
for ( size_t i = 0; i < N; i++ ) printf( "%d, %d\n", c[i][0], c[i][1] );
return 0;
}
The program output is
3, 6
2, 3
2, 1
4, 2
5, 9
If you want to write a function that will merge arrays of any size then it can look like
#include <stdio.h>
#include <stdlib.h>
#define N 5
int ** merge( int *a, int *b, size_t n )
{
int **c = malloc( n * sizeof( int * ) );
if ( c != NULL )
{
size_t i = 0;
for ( ; i < n && ( c[i] = malloc( 2 * sizeof( int ) ) ); i++ )
{
c[i][0] = a[i]; c[i][1] = b[i];
}
if ( i != n )
{
while ( i-- ) free( c[i] );
free( c );
c = NULL;
}
}
return c;
}
int main( void )
{
int a[N] = { 3, 2, 2, 4, 5 };
int b[N] = { 6, 3, 1, 2, 9 };
int **c;
c = merge( a, b, N );
if ( c != NULL )
{
for ( size_t i = 0; i < N; i++ ) printf( "%d, %d\n", c[i][0], c[i][1] );
for ( size_t i = 0; i < N; i++ ) free( c[i] );
free( c );
}
return 0;
}
The program output will be the same as shown above.

Answer 2

Really It's unclear to all. I had understood like this.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
int arrayA[5] = {3,2,2,4,5};
int arrayB[5] = {6,3,1,2,9};
int arrayC[5][5];
int i,j;
for(i=0; i<5; i++)
{
int a = arrayA[i]*10 + arrayB[i];
arrayC[i][0] = a;
}
for(i=0; i<5; i++)
{
printf("%d ", arrayC[i][0]);
printf("\n");
}
return 0;
}
After your comment:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
int arrayA[5] = {3,2,2,4,5};
int arrayB[5] = {6,3,1,2,9};
int arrayC[5];
int i,j;
for(i=0; i<5; i++)
{
arrayC[arrayA[i]] = arrayB[i];
}
for(i=0; i<5; i++)
{
printf("[%d %d]",arrayA[i], arrayC[arrayA[i]]);
printf("\n");
}
return 0;
}

Answer 3

Please edit your question and specify it (you can read https://stackoverflow.com/help/how-to-ask ).
If you know size of the array, you can create 2D array in that way:
int array[2][5] = { {2, 3, 4, 5}, {6, 3, 1, 2, 9} };
Also take a look to malloc function. This is how to create dynamic 2D array
# create array of two pointers
int **tab = (int**) malloc(sizeof(int*) * 2);
# create pointer to array
tab[0] = (int*) malloc(sizeof(int) * 5);
tab[1] = (int*) malloc(sizeof(int) * 5);
tab[0][0] = 3;
tab[0][1] = 2;
// ...
tab[1][0] = 6;
tab[1][1] = 3;
tab[1][2] = 1;
// ...
// remember to call free
free(tab[0]);
free(tab[1]);
free(tab);
Of course you should use for loop. I show you only how to create array. Please also take a look at this thread Using malloc for allocation of multi-dimensional arrays with different row lengths

Answer 4

you can do this in c++ if i get what you mean
#include <iostream>
using namespace std;
int main()
{
int arrayA[5] = {3,2,2,4,5};
int arrayB[5] = {6,3,1,2,9};
int arrayC[10];
int a=0;
int b=0;
bool use_a= true;
bool use_b = false;
for ( int i =0 ; i <10 ; i++ )
{
if(use_a){
arrayC[i]=arrayA[a];
use_a=false;
use_b= true;
a++;
}else if(use_b){
arrayC[i]= arrayB[b];
use_b=false;
use_a= true;
b++;
}
}
for(int i =0 ; i <10 ; i++)
cout<<arrayC[i];
return 0;
}