How to read two lines with a random numbers count from input into two arrays

Question

For example, input is:

12 23 32 41 45
22 11 43

lines end with '\n',

I want to save the numbers to a[] and b[];

a[] = {12, 23, 32, 41, 45}
b[] = {22, 11, 43}

The point is, I don't know how many numbers are in each line.

If I know line1 ha n numbers, and line2 has m numbers, I will use for loop:

for(int i = 0; i < n; i++) scanf("%d", a+i);
for(int i = 0; i < m; i++) scanf("%d", b+i);

Answer 1

If you would like to continue using a scanf approach, I would recommend the negated scanset %[^] format specifier.

scanf("%[^\n]", pointerToCharArray)

This should read in any number of characters up to but not including the character specified (which, in our case, is a newline). If you'd like to discard the newline, read it in as follows:

scanf("%[^\n]\n", pointerToCharArray)

More information about the negated scanset specifier.

From this point, it is a simple matter to use strtok() to tokenize the output of the scanf into number arrays.