add this three lines to your main to double check if your function works first

cout << add("2345566777844567", "9999988777765768009998") << endl; // 9999991123332545854565

cout << add("9999988777765768009998", "9999988777765768009998") << endl; // 19999977555531536019996

cout << add("2345566777844567", "745566777844567") << endl; // 3091133555689134

#include using namespace std; string add(string small, string big) { string result = ""; int carry = 0; // compare the length of the passed in variables "small" and "big" // if "small" has Zonger length than big, swap "small" and "big" // write a loop to concat 'o's to the beginning of "small" to make two strings equal length. // loop backward from the last index to index of either "big" or "small" /* Since string is char array, use big[i] and small[i] to represent each char (each digit). If you do arithmetic calculation of char, e.g. if you do 'O' + 'l', you are actually doing 48 + 49 (their ASCII values). You have to convert first. See notes. */ // int value = sum of converted big[i] and converted small[i] and carry; // if value < 10, // concat** the value to result. // set carry to o // else, // concat** the right digit of value only to the result. // set carry to 1 // Finally (outside the loop), if carry == 1 for the left-most index, add 'l' to the beginning of result. // **Note: You cannot concat int to string, so don't forget to convert int back to char when you concat. return result; int main() { // add this three lines to your main to double check if your function works first cout << add(2345566777844567","9999988777765768009998") << endl; // 9999991123332545854565 cout << add("9999988777765768009998", "9999988777765768009998") << endl; // 19999977555531536019996 cout << add("2345566777844567", "745566777844567") << endl; // 3091133555689134 // write the required loop descripted in the problem statement. cout << "End of Program." << endl; return 0