adding two array of numbers together and put it into a new array (C)

Question

I am trying to randomly generate two 30-digits array and add them up. The result has to be put into a separate new array. I am having trouble to add up two numbers together if their sum is bigger than 10. Can anyone help me?

#include <stdio.h>
#include <time.h>
#include <stdlib.h>


int main()
{
int numlist[30],numlist2[30],addnum[60],i,j,k;
srand(time(NULL));


for (i=0;i<30;i++)
{
    numlist[i] = rand()%10;

}

for (j=0;j<30;j++)
{
    numlist2[j]=rand()%10;
}

for (k=0;k<30;k++)
{

    if ((numlist[k]+numlist2[k])<10)
        addnum[k] =  numlist[k]+numlist2[k];
    else
       /*dont know what to do*/



}
return 0;
}

Hint: Result array index should not dependent on the variable looped over the array ( if you wish to keep the result sequentially in the addnum ). — Mahesh
– Mahesh, Commented Sep 24, 2014 at 21:14
first think what you've to do if the sum is not bigger than 10. you obviously have to put some kind of MARKER there so you can identify later if it was run in case of the ELSE block. — Fahad Siddiqui
– Fahad Siddiqui, Commented Sep 24, 2014 at 21:15
you guys are nuts. This is just long addition, right? How would you do it on paper? You carry the 1 to the next column. same concept. — Geoduck
– Geoduck, Commented Sep 24, 2014 at 21:17

Geoduck · Accepted Answer · 2014-09-24 21:22:44Z

1

Use a carry register:

int carry = 0;
for (k=0;k<30;k++)
{
    int adder = numlist[k]+numlist2[k]+carry;
    carry = adder/10;
    addnum[k] = adder % 10;
}
addnum[k] = carry;

answered Sep 24, 2014 at 21:22

Geoduck

9,0212 gold badges29 silver badges27 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

chux Over a year ago

Minor: A complete addition needs to continue with for (k++;k<60;k++) { addnum[k] = 0; }

Geoduck Over a year ago

ah, yes. either that or zero-init the array.

Geoduck Over a year ago

(technically, adding 2 30 digit numbers will result in at most a 31 digit number)

chux Over a year ago

True about the sum being 31 significant digits. As addnum has room for 60 digits and there is no variable indicating how many of the digits are considered significant, filling all 60 with something, even with 29 leading 0 is good practice.

Collectives™ on Stack Overflow

adding two array of numbers together and put it into a new array (C)

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related