Question

3.3 Adding big integers Write a function that adds two non-negative integers represented as strings, returning the result as a string The function must use the following signature: string add(const string& num1, const string&num2) The values num1 and num2 can represent arbitrarily long integers, so all the calculations must be done without using integer types (except for calculating each digit.) There is no need to check for or deal with strings that do not represent non-negative integers.

C== LANGUAGE. Only use iostream and string header file. A bunch of checks i am also giving that needs to be satisfied for the code to be successful

if (add("123", "456") != "579")
if (add("123", "4") != "127")

if (add("1234", "9") != "1243")
if (add("88", "12") != "100")
if (add("1234567890123456789", "10000000000000999")
!= "1244567890123457788")

string longone(120, '2');
longone[0] = '3';
string longother(123, '1');
longother[0] = '4';
longother[3] = '2';
string longresult(123, '3');
longresult[0] = '4';
longresult[1] = '1';
longresult[2] = '1';
longresult[3] = '5';

if (add(longone, longother) != longresult )

Answer 1

Here is the completed code for this problem. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks

#include<iostream>

#include<string>

using namespace std;

//required method, assuming inputs are numeric strings only

string add(const string& num1, const string num2){

                //creating an empty string to store result

                string result="";

                //variables to store the carry, sum and auxiliary digits and a character0

                int carry=0, sum, digit1, digit2;

                char chr;

                //finding last indices of both strings

                int index1=num1.length()-1;

                int index2=num2.length()-1;

                //loops as long as at least one of the indices is valid

                while(index1>=0 || index2>=0){

                                //setting digits to 0

                                digit1=0;

                                digit2=0;

                                //if index 1 is valid, extracting digit at index1 in num1 to digit1

                                if(index1>=0){

                                               //subtracting a digit by 0 returns the corresponding digit value

                                               //between 0 and 9

                                               digit1=num1[index1]-'0';

                                }

                                //doing the same for digit at num2

                                if(index2>=0){

                                               digit2=num2[index2]-'0';

                                }

                                //adding digits (and carry if any)

                                sum=digit1+digit2+carry;

                                //resetting carry

                                carry=0;

                                //if sum is greater than 9

                                if(sum>9){

                                               //storing 10th digit as carry

                                               carry=sum/10;

                                               //storing unit digit as sum

                                               sum=sum%10;

                                }

                                //adding a digit with character '0' converts an int to corresponding char value

                                //like 0 becomes '0', 1 becomes '1' etc

                                chr='0'+sum;

                                //prepending this character to result

                                result=chr+result;

                                //moving to previous indices

                                index1--;

                                index2--;

                }

                //at the end, if the carry is more than 0, prepending the carry to result

                if(carry>0){

                                chr='0'+carry;

                                result=chr+result;

                }

                return result;

}

int main(){

                //testing

                //creating two arrays of numeric strings

                string num1[]={"123","123","1234","88","1234567890123456789"};

                string num2[]={"456","4","9","12","10000000000000999"};

                //looping and adding element corresponding indices in both array

                for(int i=0;i<5;i++){

                                cout<<num1[i]<<" + "<<num2[i]<<" = "<<add(num1[i],num2[i])<<endl;

                }

                return 0;

}

/*OUTPUT*/

123 + 456 = 579

123 + 4 = 127

1234 + 9 = 1243

88 + 12 = 100

1234567890123456789 + 10000000000000999 = 1244567890123457788