Input an integer array without spaces in C

Last Updated : 13 Dec, 2018
How to input a large number (a number that cannot be stored even in long long int) without spaces? We need this large number in an integer array such that every array element stores a single digit. 
Input : 10000000000000000000000000000000000000000000000
We need to read it in an arr[] = {1, 0, 0...., 0}
In C scanf(), we can specify count of digits to read at a time. Here we need to simply read one digit at a time, so we use %1d. C 
// C program to read a large number digit by digit
#include <stdio.h>
int main()
{
    // array to store digits
    int a[100000];
    int i, number_of_digits;
    scanf("%d", &number_of_digits);
    for (i = 0; i < number_of_digits; i++) {

        // %1d reads a single digit
        scanf("%1d", &a[i]);
    }

    for (i = 0; i < number_of_digits; i++) 
        printf("%d ", a[i]);
    
    return 0;
}
Input : 
27
123456789123456789123456789
Output : 
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
We can also use above style to read any number of fixed digits. For example, below code reads a large number in groups of 3 digits. C 
// C program to read a large number digit by digit
#include <stdio.h>
int main()
{
    // array to store digits
    int a[100000];
    int i, count;
    scanf("%d", &count);
    for (i = 0; i < count; i++) {

        // %1d reads a single digit
        scanf("%3d", &a[i]);
    }

    for (i = 0; i < count; i++) 
        printf("%d ", a[i]);
    
    return 0;
}
Input : 
9
123456789123456789123456789
Output : 
123 456 789 123 456 789 123 456 789
Same concept can be used when we read from a file using fscanf()
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