my copy array function didn't work. i didn't understand why-CodePudding

This code has to copy one array to another via void copy function. But I don't understand why it doesn't work.

#include <stdio.h>

void copy(int func_array_1[], int func_array_2[], int size) {
    for (int i = 0; i < size; i  )
        func_array_1[i] = func_array_2[i];
}

int main() {

    int size = 0;
    int array[10] = { 0 };
    int copy_array[10] = { 0 };
    printf("Input the number of elements to be stored in the array :");
    scanf("%d", &size);

    for (int i = 0; i < size; i  )
        scanf("%d", &array[i]);

    copy(array, copy_array, size);

    for (int i = 0; i < size; i  )
        printf("%d", copy_array[i]);

    return 0;
}

It gives first defined array members which are all zero.

CodePudding user response：

for (int i = 0; i < size; i  )
    func_array_1[i] = func_array_2[i];

You're copying from the zero-initialized array to the one you actually want to copy to. So just change the loop body to:

func_array_2[i] = func_array_1[i];

Using const and / or more purposeful naming could've prevented your error.

CodePudding user response：

You have a typo in the function

for (int i = 0; i < size; i  )
    func_array_1[i] = func_array_2[i];      
    ^^^^^^^^^^^^^^^   ^^^^^^^^^^^^^^^

As the function is called like

copy(array, copy_array, size);

you have to write

for (int i = 0; i < size; i  )
    func_array_2[i] = func_array_1[i];      
    ^^^^^^^^^^^^^^^   ^^^^^^^^^^^^^^^

The reason of the typo is a bad function declaration. The function should be declared at least like

void copy( const int func_array_1[], int func_array_2[], int size);

That is the array that is not being changed within the function should be declared with the qualifier const.

Instead of the for loop you could use the standard function memcpy declared in the header <string.h> as for example

memcpy( func_array_2, func_array_1, size * sizeof( int ) );

Pay attention to that you need to check that the entered value of the variable size is not greater than 10.