How to make a new array with some of an existing array elements in C?

Question

I want to make a new array which contains some of elements from the first array which are greater than 5. (n is the size of the first array)

for (i = 1; i <= n; i++)
{
    if (numbers[i] > 5)
    {
        new_array[i] = numbers[i];
        printf("%d ", new_array[i]);
    }
}

If I do it like this it works perfectly and prints a new array with only those elements that are greater than 5. But if I write it like this:

for (i = 1; i <= n; i++)
{
    if (numbers[i] > 5)
    {
        new_array[i] = numbers[i];
    }
}
for (i = 1; i <= n; i++)
{
    printf("%d ", new_array[i]);
}

It doesn't work. It prints an array of n numbers and on the locations where >5 numbers were in the original array there are these numbers but on other locations there are weird numbers. How can I fix this? I want to find the minimum number in the new array and print it.

dbush · Accepted Answer · 2020-04-21 12:10:11Z

7

You're using the same index into both the old and new array. You need to keep a separate counter for each.

Also, arrays in C are zero based so you should count from 0 to n-1 instead of 1 to n.

int m = 0;
for (i = 0; i < n; i++)
{
    if (numbers[i] > 5)
    {
        new_array[m] = numbers[i];
        m++;
    }
}
for (i = 0; i < m; i++)
{
    printf("%d ", new_array[i]);
}

answered Apr 21, 2020 at 12:10

dbush

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3 Comments

OrangeBike Over a year ago

OH! you are right!! I didn't pay attention to it. Thank you so much!

OrangeBike Over a year ago

I have been trying to fix it for really long time! It's funny there was such a tiny mistake

dbush Over a year ago

@OrangeBike Glad I could help. Feel free to accept this answer if you found it useful.

Brian Makin · Accepted Answer · 2020-04-21 12:11:40Z

2

This is because the other locations have never been initialized, so could be literally anything.

You can either initialize the array beforehand or keep a separate index for your new array. For instance int j = 0; Then every time you assign to new_array increment j. This way new_array will only have the elements > 5, and you will know how many elements it holds.

answered Apr 21, 2020 at 12:11

Brian Makin

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