Multiply every other number with out using an array - c++

Question

So my problem is bigger but I just do not know what to do with my code. I can do what I want if I use an array works just fine but we are not using arrays yet so I have no idea how to do it. So I have to take user input as a string validate that the string is 16 characters long, all of them are digits, and most importantly I have to multiply every other or even character by 2. Then if it is a double digit add the two digit (ex. 10 1+0). Oh by the way I do not know why but every time I do i%2 == 0 I get the odd numbers. Is it because i is unsigned?
for(unsigned i = 1; i < card.length(); i++){
if (i % 2 == 1){
}
else {
}
}
return sum;
}

Answer 1

You could use an array of strings where each string contains a number.
Go through them checking for 2 conditions:
Double the number if it is even (i.e., i % 2 == 0)
Add the digits if the number has 2 digits (i.e., string's length is 2)
Code:
#include <iostream>
#include <iterator> using namespace std;
int TOTAL_CARDS = 16;
void printCards(string msg, string *array) {
cout<<msg<<endl;
for(int i = 0; i < TOTAL_CARDS; i++) {
cout<<"array["<<i<<"]="<<array[i]<<endl;
}
cout<<"\n"<<endl; }
int main() {
string cards[TOTAL_CARDS];
// hardcoded numbers 0 up to TOTAL_CARDS for demo purposes
for(int i = 0; i < TOTAL_CARDS; i++) {
cards[i] = to_string(i);
}
printCards("Before:", cards);
for (unsigned i = 1; i < TOTAL_CARDS; i++){
// double if even
if (i % 2 == 0){
cards[i] = to_string(stoi(cards[i]) * 2);
}
// add digits if double digit number
if (cards[i].length() == 2) {
// get each digit
string currentNum = cards[i];
int firstDigit = currentNum[0] - '0'; // char - '0' gives int
int secondDigit = currentNum[1] - '0';
// do sum and put in array
int sum = firstDigit + secondDigit;
cards[i] = to_string(sum);
}
}
printCards("After:", cards); }
Output:
Before:
array[0]=0
array[1]=1
array[2]=2
array[3]=3
array[4]=4
array[5]=5
array[6]=6
array[7]=7
array[8]=8
array[9]=9
array[10]=10
array[11]=11
array[12]=12
array[13]=13
array[14]=14
array[15]=15
After:
array[0]=0
array[1]=1
array[2]=4
array[3]=3
array[4]=8
array[5]=5
array[6]=3
array[7]=7
array[8]=7
array[9]=9
array[10]=2
array[11]=2
array[12]=6
array[13]=4
array[14]=10
array[15]=6
If you wanted to get user input for the numbers:
// get user to enter numbers
cout<<"Please enter "<<TOTAL_CARDS<<" numbers: "<<endl;
for(int i = 0; i < TOTAL_CARDS; i++) {
cin>>cards[i];
}

Answer 2

I found the answer to it. I first needed to create char variable named num. Convert the char to an int using chnum and then multiply.
for(unsigned i = 0; i < card.length(); i++){
if (i % 2 == 1){
num = card.at(i);
chnum = (num -'0');
add = chnum * 2;
if(add >= 10){
char ho = (add + '0');
string str(1,ho);
for (unsigned j = 0; j < str.length();j++){
char digi = str.at(j);
int chub = (digi - '0');
cout << digi;
//add = (chub) + (chub);
}
}
sum += add;
}